Intelligence-defined optical tunnel network system and network system control method

ABSTRACT

An intelligence-defined optical tunnel network system includes multiple Optical Switch Interconnect Sub-systems (OSIS), in which a first OSIS is configured to transmit a first lateral transmission optical signal via a first line to a second OSIS, and transmit a second lateral transmission optical signal via a second line to the second OSIS. The second OSIS includes a failover sub-module and a micro-control unit. The failover sub-module is configured to output one of the first and the second lateral transmission optical signal based on a selective signal. The micro-control unit is configured to output the selective signal to the failover sub-module to control the failover sub-module output the second lateral transmission optical signal if a signal intensity of the first lateral transmission optical signal is lower than a threshold value.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 62/683,037, filed Jun. 11, 2018, and China Application Serial Number201910146130.9, filed Feb. 27, 2019, which are herein incorporated byreference.

BACKGROUND

Data Center Networks (DCNs) are utilized in cloud data centers or edgedata centers to provide a reliable and efficient network structure,which is able to support various applications and services which arecloud-based, edge-based or enterprise-orientated, such as cloudcomputing, edge computing, data storage, data mining, social networking,etc.

In a Data Center Network utilizing conventional electrical switches fordata exchanging, a transmission rate of the Data Center Network will belimited by data exchanging capability of the conventional electronicswitches. In addition, the process of data transmission in the DataCenter Network involves a lot of Optical-Electrical conversions andElectrical-Optical conversions, which will cause a heavy powerconsumption. The conventional electronic switches also require a lot ofcomputation to determine how to route packets during the datatransmission. The computation performed by the conventional electronicswitches consumes a lot of power, increase latency of data transmissionand raise a cost to cool down the Data Center Network system.Furthermore, when a system structure of the conventional electronicswitches is formed and fixed it is difficult to upgrade the systemstructure in order to support more racks or servers with higherperformance. In order to increase a transmission rate of the Data CenterNetwork utilizing the conventional electronic switches, the existedelectronic switches are required to be replaced or upgraded, such thatit causes a higher cost to establish or maintain the Data Center Networkutilizing the conventional electronic switches.

SUMMARY

The disclosure provides an intelligence-defined optical tunnel networksystem including a plurality of optical switch interconnect sub-systems.The plurality of optical switch interconnect sub-systems comprise afirst optical switch interconnect sub-system and a second optical switchinterconnect sub-system, wherein the first optical switch interconnectsub-system transmits a corresponding first lateral transmission opticalsignal to the second optical switch interconnect sub-system through afirst line and a corresponding second lateral transmission opticalsignal to the second optical switch interconnect sub-system through asecond line, and the second optical switch interconnect sub-systemcomprises a failover sub-module and a micro-control unit. The failoversub-module is configured to output one of the first lateral transmissionoptical signal and the second lateral transmission optical signal inresponse to a selective signal. When signal intensity of the firstlateral transmission optical signal is lower than a threshold value, themicro-control unit is configured to output the selective signal to thefailover sub-module in order to control the failover sub-module tooutput the second lateral transmission optical signal.

The disclosure further provides a network system control method, whichincludes steps of: transmitting a first lateral transmission opticalsignal from a first optical switch interconnect sub-system to a secondoptical switch interconnect sub-system through a first line,transmitting a second lateral transmission optical signal from the firstoptical switch interconnect sub-system to the second optical switchinterconnect sub-system through a second line, when a signal intensityof the first lateral transmission optical signal is larger than athreshold value, outputting the first lateral transmission opticalsignal by a failover sub-module of the second optical switchinterconnect sub-system, and when the signal intensity of the firstlateral transmission optical signal is lower than the threshold value,outputting the second lateral transmission optical signal by thefailover sub-module of the second optical switch interconnectsub-system.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic diagram of an intelligence-defined optical tunnelnetwork system in accordance with some embodiments of the presentdisclosure.

FIG. 2 is a schematic diagram of an optical add-drop sub-system (OADS)in accordance with some embodiments of the present disclosure.

FIG. 3A is a connection relationship diagram of the transmission moduleof each OADS between the transmission module in the same pod inaccordance with some embodiments of the present disclosure.

FIG. 3B and FIG. 3C are schematic diagrams of the conflict caused by acombiner and the conflict caused by a demultiplexer respectively.

FIG. 3D is a schematic diagram of intra-Pods and the orientation of theoptical signal in the pod in accordance with some embodiments of thepresent disclosure.

FIG. 4 is a schematic diagram illustrating an optical switchinterconnect sub-system (OSIS) in accordance with some embodiments ofthe present disclosure.

FIG. 5 is a schematic diagram of internal design of an optical switchingsub-module in accordance with some embodiments of the presentdisclosure.

FIG. 6 is a schematic diagram of an interconnection fabric module and afailover sub-module in accordance with some embodiments of the presentdisclosure.

FIG. 7A is a schematic diagram of an interconnection network betweenoptical switch interconnect sub-systems in a second tier network inaccordance with some embodiments of the present disclosure.

FIG. 7B is a partially enlarged schematic view of FIG. 7A.

FIG. 8A is a schematic diagram of operation of a protection fabric inaccordance with some embodiments of the present disclosure.

FIG. 8B is a flow chart of the determination method of the micro-controlunit 410 in the polling mechanism in accordance with some embodiments ofthe present disclosure.

FIG. 8C and FIG. 8D are schematic diagrams of operations of themicro-control unit executing the interrupt mechanism in accordance withsome embodiments of the present disclosure.

FIG. 9 is a schematic diagram of inter-Pods optical tunnel paths betweenthe pods in accordance with some embodiments of the present disclosure.

FIG. 10A and FIG. 10B are schematic diagrams of setup of the opticalswitching sub-modules of the optical switch interconnect sub-system,respectively, in accordance with some embodiments of the presentdisclosure.

FIG. 11A is a schematic diagram of a design of a protection path in thepod of the first tier network in accordance with some embodiments of thepresent disclosure.

FIG. 11B is a schematic diagram of a design of a protection path in thepod of the first tier network T1 in accordance with some embodiments ofthe present disclosure.

FIG. 12 is a schematic diagram of a design of a protection path betweenthe first tier network and the second tier network in accordance withsome embodiments of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentdisclosure, examples of which are described herein and illustrated inthe accompanying drawings. While the disclosure will be described inconjunction with embodiments, it will be understood that they are notintended to limit the disclosure to these embodiments. On the contrary,the disclosure is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of thedisclosure as defined by the appended claims. It is noted that, inaccordance with the standard practice in the industry, the drawings areonly used for understanding and are not drawn to scale. Hence, thedrawings are not meant to limit the actual embodiments of the presentdisclosure. In fact, the dimensions of the various features may bearbitrarily increased or reduced for clarity of discussion. Whereverpossible, the same reference numbers are used in the drawings and thedescription to refer to the same or like parts for better understanding.

The terms used in this specification and claims, unless otherwisestated, generally have their ordinary meanings in the art, within thecontext of the disclosure, and in the specific context where each termis used. Certain terms that are used to describe the disclosure arediscussed below, or elsewhere in the specification, to provideadditional guidance to the practitioner skilled in the art regarding thedescription of the disclosure.

The terms “comprise,” “comprising,” “include,” “including,” “has,”“having,” etc. used in this specification are open-ended and mean“comprises but not limited.” As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed items.

In this document, the term “coupled” may also be termed “electricallycoupled” and “coupled by optical fiber”, and the term “connected” may betermed “electrically connected” and “connected by optical fiber”.“Coupled” and “connected” may also be used to indicate that two or moreelements cooperate or interact with each other. It will be understoodthat, although the terms “first,” “second,” etc., may be used herein todescribe various elements, these elements should not be limited by theseterms. These terms are used to distinguish one element from another. Forexample, a first element could be termed a second element, and,similarly, a second element could be termed a first element, withoutdeparting from the scope of the embodiments. In this disclosure,mentioned terms 1×1, 1×2, 1×3, 2×1, 2×2, 5×1, 6×4 and N×M illustrate theamount of input terminals and the amount of output terminals such as 1input and 1 output, 1 input and 2 outputs, 1 input and 3 outputs, 2inputs and 1 output, 2 inputs and 2 outputs, 5 inputs and 1 output, 6inputs and 4 outputs, and N inputs and M outputs respectively.

Please refer to FIG. 1. FIG. 1 is a schematic diagram of anintelligence-defined optical tunnel network system 100 in accordancewith some embodiments of the present disclosure. In some embodiments,the intelligence-defined optical tunnel network system 100 can beapplied to the intelligence-defined optical tunnel network system(OPTUNS) in the Edge Data Center for replacing the complicated,multi-tier and electrically-switching network system in the data center.

As shown in FIG. 1, in some embodiments, the intelligence-definedoptical tunnel network system 100 includes a first tier network T1 and asecond tier network T2. The first tier network T1 and the second tiernetwork T2 can be interconnected by a single mode fiber. In someembodiments, the first tier network T1 and the second tier network T2are optical switching networks respectively.

As shown in FIG. 1, in some embodiments, the first tier network T1includes a plurality of pods, as the pods P1-P4 shown in the figure. Inthis embodiment, the pods P1-P4 are pods of optical nodes respectively.For ease of understanding and simplifying the description, some pods ofthe first tier network T1 is not shown in FIG. 1.

Any one of the pods P1-P4 in the first tier network T1 includes aplurality of optical add-drop sub-systems (OADS) 200 a-200 e as opticalnodes. OADSs are configured to transmit data, through a plurality of Topof Rack (ToR) switches ToRa and ToRb respectively, with servers in acorresponding plurality of racks 900 a and 900 b. As shown in FIG. 1, insome embodiments, each pod P1-P4 includes five OADSs respectively. Forease of description, there are only two sets of ToR switches ToRa, ToRband racks 900 a, 900 b illustrated in the diagram.

In practice, the remaining OADSs are also connected to theircorresponding servers through the corresponding ToR switches in order toperform data transmission. Further, the amount of OADSs included in eachpod P1-P4 can be adjusted according to the actual requirement. FIG. 1 ismerely exemplary and the present disclosure is not limited thereto.

Taking the OADS 200 a as an example, any one of the OADSs in the pod P1includes a first transmission module 210 and a second transmissionmodule 220. The first transmission module 210 is configured to performdata transmission at a first frequency band. The second transmissionmodule 220 is configured to perform data transmission at a secondfrequency band differed to the first frequency band. In someembodiments, the first transmission module 210 and the secondtransmission module 220 are optical transmission module respectively.The first frequency band is a wavelength band in a specific wavelengthrange, and the second frequency band is another wavelength band inanother specific wavelength range. As shown in FIG. 1, in the same podP1, the first transmission module of any one of the OADS (i.e., OADS 200a) is connected to the first transmission modules 210 of the adjacentthe OADS (i.e., OADS 200 b) to form a first transmission ring.Similarly, the second transmission module of any one of the OADS (i.e.,OADS 200 a) is connected to the second transmission modules 220 of theadjacent the OADS (i.e., OADS 200 b) to form a second transmission ring.In some embodiments, the first transmission modules 210 in the firsttransmission ring are connected to each other through an optical fiber,and the second transmission modules 220 in the second transmission ringare connected to each other through an optical fiber.

It should be noted that, in some embodiments, the first frequency bandsconfigured in the first transmission modules of each OADSs 200 a-200 ein the same pod are different from each other, and the second frequencybands configured in the second transmission modules of each OADSs 200a-200 e are different from each other. The detail of the module,frequency band configuration and specific operation of the OADSs 200a-200 e will be described in the following paragraphs with thecorresponding diagrams.

As shown in FIG. 1, in some embodiments, the second tier network T2comprises a plurality of optical switch interconnect sub-systems (OSIS)400 a-400 e as optical nodes. Structurally, any two of the OSISs 400a-400 e transmits a corresponding lateral transmission optical signalthrough the corresponding first line to implement communication betweeneach of the OSISs 400 a-400 e. In other words, the OSISs 400 a-400 e areinterconnected to each other with optical fiber in a structure which issimilar to the mesh network, so that the fiber network between any pairof OSISs 400 a-400 e and the fiber network between any other pair of theOSISs 400 a-400 e operate independently to each other. In someembodiments, the optical fiber network between the OSISs 400 a-400 e canbe implemented with ribbon fiber. Therefore, the connection between theOSISs 400 a-400 e also appears to be a ring-shaped mesh structure R2 inoutward expression.

The OSISs 400 a-400 e are configured to receive, respectively, opticalsignals from the OADS of the first tier network T1, after performingroute switching and optical wavelength switching transit downwardly toanother OADS of the first tier network T1.

A Software-defined network controller (SDN controller) 500 is configuredto output corresponding control signals to each of the ToR switchesToRa, ToRb, the OADSs 200 a-200 e and the OSISs 400 a-400 e in order tobuild optical tunnels and schedule the optical tunnels. Thus, the datatransmission in the system between each server can be implemented byutilizing optical signals through the optical fiber networks in thefirst tier network T1 and the second tier network T2.

It should be noted that the amounts of OSISs and of OADSs illustrated inFIG. 1 are merely exemplary and the present disclosure is not limitedthereto. In various embodiments, the amount of OSISs 400 a-400 e andOADSs 200 a-200 e of the intelligence-defined optical tunnel networksystem 100 can be incrementally increased and/or decreased in accordancewith the actual requirement and the normal operation of theintelligence-defined optical tunnel network system 100 is maintained.Therefore, the intelligence-defined optical tunnel network system 100has a high degree of deployment flexibility.

As a result, in the intelligence-defined optical tunnel network system100, by selecting a particular wavelength combination of the OSISs 400a-400 e, the OADSs 200 a-200 e and the optical signals, the opticaltunnel (that is, the optical path pluses optical wavelength combination)for data exchange between racks and racks can be established to achievea ultra-low latency of data transmission.

In addition, in some embodiments, the dense wavelength divisionmultiplexing (DWDM) technology can be applied in theintelligence-defined optical tunnel network system 100. By utilizingDWDM transceiver, various optical wavelengths can be used fortransmitting data at the same time in the intelligence-defined opticaltunnel network system 100. However, intelligence-defined optical tunnelnetwork system 100 in the present disclosure is not limited to DWDMtechnology. The intelligence-defined optical tunnel network system 100may also be implemented with other wavelength division multiplexing(WDM) or other equivalent multiplexed optical transmission technology.In this way, the intelligence-defined optical tunnel network system 100can achieve low latency, high bandwidth, low power consumption, and hasbetter performance than the electrically-switching network system usedin the existing data center.

For ease of description, the following paragraphs are the descriptionwith the relevant diagrams for the OADSs 200 a-200 e of the first tiernetwork T1 and the design of its network structure, the OSISs 400 a-400e of the second tier network T2 and the design of its network structure,the design of interconnect structure between the first tier network T1and the second tier network T2, the design of protection path of thefirst tier network T1 and the design of protection path of the secondtier network T2.

Please refer to FIG. 2. FIG. 2 is a schematic diagram of the OADS 200 inaccordance with some embodiments of the present disclosure. The OADS 200is a core switch node for building optical tunnels between the racks ofthe first tier network T1 for data transmission. As shown in FIG. 2, theOADS 200 includes two or more independent transmission modules, such asa first transmission module 210 and a second transmission module 220.The first transmission module 210 and the second transmission module 220use different wavelength band sequentially. In some embodiments, thewavelength bands used by the first transmission module 210 and thesecond transmission module 220 are adjacent to each other. Specifically,the wavelength band is a plurality of specific wavelength combinationsarranged ascendingly by their frequency (i.e., frequency equals to thespeed of light divided by wavelength).

As shown in FIG. 2, the first and second transmission modules 210 and220, respectively, include multiplexers 212 and 222 as inputsub-modules. In addition, the first and second transmission modules 210and 220, respectively, include switching sub-modules 214 and 224 anddemultiplexers 216 and 226 as output sub-modules. Specifically, theswitching sub-module 214 in the first transmission module 210 includes afirst splitter SP11, a second splitter SP12, an optical signal amplifierEFDA1, a first wavelength selective switch WSS11, and a secondwavelength selective switch WSS12. Similarly, the switching sub-module224 of the second transmission module 220 also includes a third splitterSP21, a fourth splitter SP22, an optical signal amplifier EFDA2, a thirdwavelength selective switch WSS21, and a fourth wavelength selectiveswitch WSS22. The multiplexer 222 (the function and operation of whichcan be referred to the multiplexer 212 of the first transmission module210 in the following embodiment), connected to the corresponding one ofthe ToRs, is configured to receive, through a plurality of add-ports, aplurality of second upstream optical signals (UL9-UL16) from the ToRswitch, and combine the second upstream optical signals (UL9-UL16) intoa second composite optical signal Sig21. The third splitter SP21 (thefunction and operation of which can be referred to the first splitterSP11 of the switching sub-module 214 in the following embodiment),deposited on the second transmission ring Ring2, is configured toreceive and duplicate the second composite optical signal Sig21 as afifth lateral transmission optical signal TSh5 and a third uplinktransmission optical signal TSu3, transmit the fifth lateraltransmission optical signal TSh5 through the second transmission ringRing2 to the second transmission module 220 of another OADS in the samepod and transmit the third uplink transmission optical signal TSu3through a second longitudinal port 221. The optical signal amplifierEFDA2 (the function and operation of which can be referred to theoptical signal amplifier EFDA1 of the switching sub-module 214 in thefollowing embodiment), deposited on the second transmission ring Ring2and connected to the third splitter SP21, is configured to amplify thefifth lateral transmission optical signal TSh5 and output the amplifiedfifth lateral transmission optical signal TSh5′ to the secondtransmission module 220 of another OADS in the same pod. The fourthsplitter SP22 (the function and operation of which can be referred tothe second splitter SP12 of the switching sub-module 214 in thefollowing embodiment), deposited on the second transmission ring Ring2,is configured to receive and duplicate the fifth lateral transmissionoptical signal TSh5′, received from the second transmission module 220of another OADS in the same pod, as a third downlink transmissionoptical signal TSd3 and a sixth lateral transmission optical signalTSh6, and transmit the sixth lateral transmission optical signal TSh6through the second transmission ring Ring2. The third wavelengthselective switch WSS21 (the function and operation of which can bereferred to the first wavelength selective WSS11 of the switchingsub-module 214 in the following embodiment), coupled to the secondtransmission ring Ring2, is configured to receive the third downlinktransmission optical signal TSd3 from the fourth splitter SP22 orreceive a fourth downlink transmission optical signal TSd4 from the OSIS400 e, and selectively output the third downlink transmission opticalsignal TSd3 or the fourth downlink transmission optical signal TSd4. Thefourth wavelength selective switch WSS22 (the function and operation ofwhich can be referred to the second wavelength selective WSS12 of theswitching sub-module 214 in the following embodiment), disposed on thesecond transmission ring Ring2, is configured to receive the sixthlateral transmission optical signal TSh6 and output a seventh lateraltransmission optical signal TSh7 to the third splitter SP21. The thirdsplitter SP21 is further configured to receive and duplicate the seventhlateral transmission optical signal TSh7 as an eighth lateraltransmission optical signal TSh7 d and a fourth uplink transmissionoptical signal TSu4, transmit through the second transmission ring Ring2the eighth lateral transmission optical signal TSh7 d, and transmit,through the second longitudinal port 221, the fourth uplink transmissionoptical signal TSu4 to the OSIS 400 e. When the optical path from theOADS 200 a to the OADS 200 b on the first transmission ring Ring1 is cutoff, the software-defined network controller 500 sets up correspondinglythe ToR switch, the third wavelength selective switch WSS21 and thefourth wavelength selective switch WSS22 of the second transmissionmodule 220 in order to build the optical tunnel from the OADS 200 a tothe OADS 200 b on the second transmission ring Ring2.

The multiplexer 212 is as an input sub-module of the first transmissionmodule 210. Similarly, the multiplexer 222 is as an input sub-module ofthe second transmission module 220. In structure, the multiplexer 212,222 are connected to the one (i.e., ToR switch), corresponding to theOADS 200, of the ToR switches. The multiplexer 212, 222 having aplurality of add-ports, are configured to receive a plurality of firstupstream optical signals UL1-UL8, a plurality of second upstream opticalsignals UL9-UL16, and combine the first upstream optical signals UL1-UL8and the second upstream optical signals UL9-UL16 into a first compositeoptical signal Sigh 1 and a second composite optical signal Sig21.

Specifically, each add-port of the multiplexers 212 and 222 is coupledwith optical fiber to a transmitter of the various DWDM transceivers onan input-output port of ToR switch in the rack, in which the DWDMtransceiver is corresponding to the wavelength band of the add-port. Insome embodiments, each add-port of the multiplexer 212 and 222 areconfigured to receive signals with a fixed wavelength. One add-port onthe multiplexer 212 or 222 receives a signal with one specificwavelength.

As shown in FIG. 2, the first upstream optical signals UL1-UL8 have aplurality of wavelengths λ1-λ8 in the first frequency band respectively.Similarly, the second upstream optical signals UL9-UL16 have a pluralityof wavelengths λ9-λ16 in the second frequency band respectively. In thisway, the multiplexers 212 and 222 can receive, from the ToR switch, theoptical signals of the wavelength band (i.e., wavelength λ1-λ8 andλ9-λ16) configured in the first transmission module 210 and the secondtransmission module 220, and combine the different optical wavelengthsignals into one optical fiber in order to be transmitted as the firstcomposite optical signal Sig11 and the second composite optical signalSig21.

The switching sub-module 214 of the first transmission module 210includes the first splitter SP11, the optical signal amplifier EDFA1,the second splitter SP12, the first wavelength selective switch WSS11,and the second wavelength selective switch WSS12. Similarly, the secondtransmission module 220 of the switching sub-module 224 also includesthe third splitter SP21, the optical signal amplifier EDFA2, the fourthsplitter SP22, the third wavelength selective switch WSS21, and thefourth wavelength selective switch WSS22.

The main function of the switching sub-modules 214 and 224 is tosuccessively upload the first composite optical signal Sig11 and thesecond composite optical signal Sig21 transmitted from the inputsub-module (i.e., the multiplexers 212 and 222) to the OSIS 400 a and400 e in the second tier network T2 or transmit, to East or West, to theother OADS 200 in same pod, and switch the optical signals transmittedfrom the other OADS 200 in same pod to the input sub-module 216 and 226.For example, the OADSs in the pod P2 in FIG. 1 can transmit/receive theoptical signals to/from the other four OADSs in the same pod P2. In thesame principle, the OADSs in each pod in FIG. 1 can transmit/receive theoptical signals to/from the other four OADSs in the same pod.

For ease of explanation, in the following paragraphs, the firsttransmission module 210 will be taken as an example to describe theoperation of each component. The components in the second transmissionmodule 220 and the operation of the second transmission module 220 aresimilar to the first transmission module 210, and thus are not describedherein.

As shown in FIG. 2, in structure, the first splitter SP11, disposed onthe first transmission ring Ring1, is configured to receive andduplicate the composite optical signal SP11 as a first lateraltransmission optical signal TSh1 and a first uplink transmission opticalsignal TSu1, transmit through the first transmission ring Ring1 thefirst lateral transmission optical signal TSh1, and transmit, throughthe first longitudinal port 211, the first uplink transmission opticalsignal TSu1 to the OSIS 400 a.

In some embodiments, the optical signal amplifier EDFA1 can beimplemented with erbium-doped fiber amplifier (EDFA). The optical signalamplifier EDFA1, disposed on the first transmission ring Ring1 andcoupled to the first splitter SP11, is configured to amplify the firstlateral transmission optical signal TSh1 and output the amplified firstlateral transmission optical signal TSh1′ to the first transmissionmodule 210 of other OADSs in the same pod. Therefore, in the embodimentshown in FIG. 2, the optical signal amplifier EDFA1 can amplify thepower of the optical signal transmitted to the West to ensure that ithas sufficient power to be transmitted to the destination, but thepresent disclosure is not limited in the direction of transmission tothe West. In actual applications, the transmission direction can beadjusted according to the network configuration.

As shown in FIG. 2, in structure, the second splitter SP12 disposed onthe first transmit ring Ring1, is configured to receive and duplicate afirst lateral transmission optical signal TSh1′, received from the firsttransmission module 210 of other OADSs 200 in the same optical node pod,as a first downlink transmission optical signal TSd1 and a secondlateral transmission optical signal TSh2, and transmit the secondlateral transmission optical signal TSh2 through the first transmissionring Ring1.

The first wavelength selective switch WSS11, coupled to the firsttransmission ring Ring1, configured to receive the first downlinktransmission optical signal TSd1 from the second splitter SP12 orreceive a second downlink transmission optical signal TSd2 from the OSIS400 a, and selectively output the first downlink transmission opticalsignal TSd1 or the second downlink transmission optical signal TSd2 asthe composite optical signal Sig12 to the demultiplexer 216.

Specifically, the first wavelength selective switch WSS11 is a 2×1 (2input and 1 output) wavelength selective switch, being configured toselect specific wavelength signal to pass in order to output thecorresponding optical signal to the demultiplexer 216. In someembodiments, the 2×1 wavelength selective switch can be implemented byincluding two 1×1 wavelength selective switches and one 2×1 combiner,integrating, through the combiner, two optical signals selected by two1×1 wavelength selective switches and outputting the combined compositeoptical signal Sig12 to the demultiplexer 216 of the receivingsub-module.

The second wavelength selective switch WSS12, disposed on the firsttransmission ring Ring1, configured to receive the second lateraltransmission optical signal TSh2 and output a third lateral transmissionoptical signal TSh3 to the first splitter SP1. The first splitter SP1 isfurther configured to receive and duplicate the third lateraltransmission optical signal TSh3 as a fourth lateral transmissionoptical signal TSh3 d and a second uplink transmission optical signalTSu2. The fourth lateral transmission optical signal TSh3 d istransmitted through the first transmission ring Ring1 by the firstsplitter SP11 and the second uplink transmission optical signal TSu2 istransmitted through the first longitudinal port 211 by the firstsplitter SP11 to the OSIS 400 a.

In other words, the first splitter SP11 is a 2×2 (2 input 2 output)splitter, and includes two input ports and two output ports, one ofwhich is configured to receive the first composite optical signal Sig11.The first splitter SP11 is configured to duplicate the received firstcomposite optical signal Sig11 to the two output ports. The other inputport is configured to receive the third lateral transmitted opticalsignal TSh3. The first splitter SP11 is configured to duplicate thethird lateral transmission optical signal TSh3 to the two output ports.One output port of the first splitter SP11 is configured to output thefirst lateral transmission optical signal TSh1 or the fourth lateraltransmission optical signal TSh3 d, and the other output port isconfigured to output the first uplink transmission optical signal TSu1or the second uplink transmission optical signal TSu2. The secondsplitter SP12 is 1×2 (1 input and 2 output) splitter and duplicates andsplits the first lateral transmission optical signal TSh1′, receivedfrom the first transmission module 210 of other OADSs in the sameoptical node pod, into two beams. In the embodiment shown in FIG. 2, inwhich one as the second lateral optical transmission optical signal TSh2is transmitted continually to the West to other OADSs in the same pod P1and the other as the first downlink transmission optical signal TSd1 istransmitted downwardly to the optical receiving module (i.e., thedemultiplexer 216). However, the present disclosure is not limited inthe direction of transmission to the West. In actual applications, thetransmission direction can be adjusted according to the networkconfiguration.

The second lateral transmission optical signal TSh2 passes through the1×1 second wavelength selection switch WSS12, and the second wavelengthselection switch WSS12 selects the specific optical wavelength signal ofthe second lateral transmission optical signal TSh2 as the third lateraltransmission optical signal TSh3. Then, through the first splitter SP11duplicating and splitting, in the embodiment shown in FIG. 2, oneoptical signal as the fourth lateral transmission optical signal TSh3 dis transmitted continually to the West to the other OADSs in the sameoptical node pod, and the other optical signal as the second uplinktransmission optical signal TSu2 is output to the corresponding OSIS 400a. However, the present disclosure is not limited in the direction oftransmission to the West. In actual applications, the transmissiondirection can be adjusted according to the network configuration.

Please refer to the FIG. 3A together. FIG. 3A is a connectionrelationship diagram of the first transmission module 210 and the secondtransmission module 220 of each OADSs 200 a-200 e in the same pod inaccordance with some embodiments of the present disclosure.

It should be noted that, as shown in FIG. 3A, in some embodiments, thefirst transmission module 210 and the second transmission module 220 ofeach of the OADSs 200 a-200 e transmit, through the first transmissionring Ring1 and the second transmission ring Ring2 respectively, thelateral transmission optical signals TSh1-TSh3 and TSh3 d. The opticaltransmission directions in the first transmission ring Ring1 and thesecond transmission ring Ring2 are opposite to each other. For example,each of the first transmission modules 210 transmits signals in aWestward direction (i.e., a clockwise direction) with the firsttransmission ring Ring1, and each of the second transmission modules 220transmits signals eastward (i.e., counter-clockwise direction) with thesecond transmission ring Ring2. But the disclosure is not limitedthereto. In other embodiments, the first transmission ring Ring1 and thesecond transmission ring Ring2 can also transmit the lateraltransmission optical signals TSh1-TSh3 and TSh3 d in the same opticaltransmission direction.

In addition, as shown in FIG. 3A, the first transmission module 210 ofthe OADSs 200 a-200 e are coupled to the OSIS 400 a through a pluralityof corresponding first longitudinal ports (shown by solid arrows in thefigure) respectively. The second transmission module 220 of the OADSs200 a-200 e are coupled to, through a plurality of corresponding secondlongitudinal ports (shown by dashed arrows in the figure), the OSIS 400e which is adjacent to the OSIS 400 a.

Please refer back to FIG. 2 again. As shown in FIG. 2, the demultiplexer216 and 226 are as output sub-modules of the OADS 200. Structurally, thedemultiplexer 216 and 226 are coupled to, respectively, the firstwavelength selective switch WSS11 and WSS21, connected to thecorresponding one of the ToR switches, are configured to receive anddemultiplex the first downlink transmission optical signal TSd1 or thesecond downlink transmission optical signal TSd2 as a plurality ofdownstream optical signals DL1-DL8 and DL9-DL16 and transmit thedownstream optical signals DL1-DL8 and DL9-DL16 to the ToR switch.

Specifically, the demultiplexer 216 and 226 including cyclic DEMUXindividually, are configured to receive the composite optical signalSig12 and Sig 22, which include each wavelength, from the wavelengthselective switch WSS11 and WSS21, and selectively filter the opticalsignals with a specific wavelength to pass to enter a correspondingdrop-port. For example, it is assumed that the intelligence-definedoptical tunnel system totally uses 40 kinds of wavelength (which arearranged in ascending frequency λ1-λ40), and each wavelength bandincludes eight wavelengths, each individual first transmission module210 and second transmission module 220 including eight drop-ports.Therefore, The cyclic DEMUX having eight channels may arrange the comingat most 40 wavelengths in order according to the period, and select thewavelength signal, by the wavelength selective switch WSS11 and WSS21,to enter into the demultiplexer 216 and 226. The eight wavelengthsselected by the wavelength selective switch WSS11 and WSS21 enter into,individually, the corresponding eight drop-ports of the demultiplexer216 of the first transmission module 210, in which only onecorresponding wavelength signal been selected enters each drop-port atthe same time. For instance, in one embodiment, the wavelengthconfiguration of the cyclic demultiplexer is shown in table 1 below:

TABLE 1 (Wavelength Configuration of the Cyclic Demultiplexer) Drop-portreceived wavelength 1 λ1 λ9 λ17 λ25 λ33 2 λ2 λ10 λ18 λ26 λ34 3 λ3 λ11λ19 λ27 λ35 4 λ4 λ12 λ20 λ28 λ36 5 λ5 λ13 λ21 λ29 λ37 6 λ6 λ14 λ22 λ30λ38 7 λ7 λ15 λ23 λ31 λ39 8 λ8 λ16 λ24 λ32 λ40

As shown in Table 1 in the present embodiment, the first wavelength ofeach wavelength band (λ1, λ9, λ17, λ25, λ33) enters into the firstdrop-port, the second wavelength (λ2, λ10, λ18, λ26, λ34) enters intothe second drop-port, and so on. Each drop-port is connected to theoptical fiber to a receiver of the DWDM transceivers on an input-outputport of ToR switch in the rack, in which the DWDM transceiver iscorresponding to the module wavelength band of the drop-port. Forexample, the first drop-port may be connected to the receiver of theDWDM transceiver with the first wavelength λ1 in the frequency band ofthe input-output port of ToR switch in the rack. In this way, eachdrop-port of the demultiplexer 216 and 226 can receive a plurality ofoptical signals with wavelength cyclic number.

It should be noticed that, if the optical signals with the samewavelength are transmitted through the same optical fiber of the firsttransmission module 210 and the second transmission module 220 at thesame time, the interference of signals may raise to cause conflict.Please refer to FIG. 3B and FIG. 3C together. FIG. 3B and FIG. 3C areschematic diagrams of the conflict caused by a combiner and the conflictcaused by a demultiplexer respectively. As shown in FIG. 3B, when thefirst wavelength selective switch WSS11 receives the first downlinktransmission optical signal TSd1 from the second splitter SP12, andreceives the optical signals, including the same wavelength (i.e., λ1),in the second downlink transmitted optical signal TSd2 from the OSIS 400a, and if the two 1×1 wavelength selective switches in the 2×1 firstwavelength selective switch WSS11 select λ1 to pass, the two opticalsignals with the wavelength λ1 may be combined simultaneously to oneoptical fiber through the 2×1 combiner and output to the demultiplexer216 to cause conflict.

As shown in FIG. 3C, the second type of conflict is a conflict caused bythe demultiplexer 216. Due to the design of the cyclic demultiplexer,each drop-port may receive five kinds of wavelength arranged accordingto the order of the wavelength cycle (shown in the preceding table 1).It is assumed that the first wavelength selective switch WSS11 receivesthe first downlink transmission optical signal TSd1 from the secondsplitter SP12, and the second downlink transmission optical signal TSd2the OSIS 400 a, and selects, respectively, the optical signal withwavelength λ1 in the first downlink transmission optical signal TSd1 andthe optical signal with wavelength λ9 in the second downlinktransmission optical signal TSd2 to pass. Even though the two beams withdifferent wavelengths can be combined into one optical fiber as thecomposite optical signal Sig12 successfully and transmitted to thedemultiplexer 216, after passing through the demultiplexer 216, theoptical signal with wavelength λ1 and with wavelength λ9 may beintroduced into the same drop-port (i.e., the first drop-port). Finally,the optical signal wavelength with λ1 and with wavelength λ9 may arriveat the same receiver of the DWDM transceiver. Because the receiver ofthe same DWDM transceiver can only receive one wavelength signal at thesame time, otherwise the interference may occur. A conflict will occurat this point. Thus, in some embodiments, due to the design of thereceiving of the demultiplexer 216, even two optical tunnels usingdifferent wavelengths λ1, λ9 may cause conflicts. Therefore, performingthe tunnel scheduling control of the optical tunnel network through thesoftware-defined network controller (SDN Controller) 500 is needed toprevent conflict conditions occur and optimize the utilization rate ofthe optical tunnel network.

The description above is for the internal modules and operations of theOADS 200. Then, the following paragraphs are the description for thedesign of the network structure of the interconnection of the OADSs 200a-200 e to form the pod P1. Please refer to FIG. 3A again. As shown inFIG. 3A, the OADSs 200 a-200 e form a pod P1 with optical fiberconnection in series. As described above, an amount of the OADSs 200a-200 e being connected in series in one pod depends on the amount ofwavelengths configured in each independent first transmission module 210and a second transmission module 220 and the total amount of wavelengthtypes supported by the intelligence-defined optical tunnel networksystem 100. The first transmission module 210 and the secondtransmission module 220 of each OADSs 200 a-200 e may be connected inseries to the corresponding first transmission module 210 and the secondtransmission module 220 of adjacent OADS 200 a-200 e, forming aring-shaped network. Therefore, a pod will include a plurality ofindependent ring networks.

The frequency band wavelength used by each transmission module (i.e.,the first transmission module 210) belonging to the same transmissionring (i.e., the first transmission ring Ring1) cannot be repeated toeach other and be arranged in counterclockwise ascendingly according tothe wavelength frequency. In addition, because the transmission ringsare independent of each other, the same wavelength can be reused ondifferent rings. Alternately, in some embodiments, the types and amountsof wavelengths used on the first transmission ring Ring1 and the secondtransmission ring Ring2 are the same.

Taking structure of the pod P1 in FIG. 3A as an example, two opticalfibers are used to connect in series the corresponding firsttransmission module 210 and the second transmission module 220 in theOADSs 200 a-200 e respectively. Among them the first transmission ringRing1 transmits the optical signal to the West (i.e., a clockwisedirection), and the second transmission ring Ring2 transmits the opticalsignal to the East (i.e., counterclockwise direction). The firsttransmission module 210 of the first OADS 200 a in the firsttransmission ring Ring1 uses the frequency band including wavelengthλ1-λ8. The first transmission module 210 of the next OADS 200 e in theEast uses the frequency band including wavelength λ9-λ16. The firsttransmission module 210 of the one after next OADS 200 e in the Eastuses the frequency band including wavelength λ17-λ24, and so on.

It should be noticed particularly, the wavelength frequency band used byeach second transmission module 220 in the second transmission ringRing2 may be shifted and adjacent to the one used by the firsttransmission module 210. For example, the second transmission module 220of the first OADS 200 a uses wavelength λ9-λ16 (shifted and adjacent tothe wavelength λ1-λ8 used by the first transmission module 210 of theOADS 200 a). The second transmission module 220 of the next OADS 200 ein the East uses wavelength λ17-λ24 (shifted and adjacent to thewavelength λ9-λ16 used by the first transmission module 210 of the OADS200 e). The second transmission module 220 of the one after the nextOADS 200 d in the East uses wavelength λ25-λ32, and so on. In otherwords, In the same pod P1, the first frequency band configured in thefirst transmission module 210 in the OADS 200 a and the second frequencyband configured in the second transmission module 220 in the OADS 200 binclude same wavelength combination.

Such a configuration allows each of the OADSs 200 a-200 e to support 16wavelength bandwidths. The maximum amount of OADS 200 that can beconnected in series in a pod P1 depends on the type of wavelength usedby the system. Taking the structure in FIG. 1 as an example, assumingthe intelligence-defined optical tunnel network system 100 supports atotal of 40 kinds of wavelengths, then five independent series moduleswith different wavelength bands can be connected in series on anindependent ring. It is equivalent to connecting five OADSs 200 a-200 e(as shown in FIG. 3A) in series in one pod P1.

In addition, the types and amounts of transmission wavelengths used ineach of the transmission rings Ring1 and Ring2 are the same, so fortywavelengths (λ1-λ40) are used in the first transmission ring Ring1, andthe second transmission ring Ring2 is also used λ1-λ40. In thisring-shape design structure, an OADSs 200 a-200 e can transmit theoptical signals to East or West and receive the optical signals from theother OADS in the same pod P1.

In addition, the pod ring network structure includes two designfeatures, which are the incremental structure design and feature ofwavelength reuse. The specific content will be described in detail inthe following paragraphs.

The spirit of the incremental structure design is manifested in twodeployment modes. The first one is to gradually increase and concatenatethe nodes of the required OADSs 200 a-200 e in a pod according to therequired amount of racks. The second is to gradually increase the amountof independent transmission rings Ring1 and Ring2 in a pod P1.

For example, since the OADS utilizes a modular design, and each pod ofthe first tier network T1 utilizes a ring-shaped design structure, it ispossible to connect different amounts of OADSs 200 a-200 e in one podflexibly. In other words, as the demand increases, the required OADSs200 a-200 e can be gradually added and concatenated in a pod accordingto the required amount of racks. For example, when the amount ofrequired racks is small (i.e., three racks), there can be only threeOADSs 200 a-200 c connected in a ring-shape series in pod P1. When theamount of required racks increases (i.e., five racks), the pod P1 can beexpanded to include five OADSs 200 a-200 e in a ring-shaped series.

In addition, the amount of independent transmission rings Ring1 andRing2 can be added in the same pod. For example, when the amount ofservers in the rack increases or the bandwidth is upgraded, the networktraffic load generated on behalf of the entire rack also risesrelatively. There are two ways to solve this situation. The first methodis that when the amount of wavelengths used by the OADSs 200 a-200 e isthe same, based on a characteristic of data rate transparency of theintelligence-defined optical tunnel network system, the DWDM transceiverwith higher speed data rate can be used instead to support the networktraffic load generated on behalf of the increasing amount of the serversor the upgrade of the bandwidth. For example, the transmission speed ofeach wavelength may upgrade to from 10 Gbit/s to 100 Gbit/s to increasethe flexibility of application of the system transmission rate and savethe mass cost for upgrading hardware devices.

The second method is that when the transmission speed of wavelength isthe same, the amount of transmission modules in the OADS 200 can begradually increased to increase the amount of wavelengths that can beselectively used by the racks. Since the transmission modules areindependent of each other, it is equivalent to gradually increasing theamount of transmission rings in one pod to support the network trafficload generated by the increase in the amount of servers in the rack orthe bandwidth upgrade. An amount of independent transmission ring can beformed in one pod depends on the amount of wavelengths used byindependent transmission modules and the type of wavelength used by thesystem. For example, when the intelligence-defined optical tunnelnetwork system 100 uses 40 kinds of wavelength, one OADS 200 can includeat most five independent modules with a different frequency band, usingbands of λ1-λ8, λ9-λ16, λ17-λ24, λ25-λ32, and λ33-λ40 respectively.Correspondingly, one pod can form at most five transmission rings.

In other words, in some embodiments, any one of the OADS 200 may includeN pieces of the transmission modules independent of each other; so thatthe OADSs in the same pod can be connected to each other through arespective N transmission rings. N transmission modules of one OADS 200are coupled to two adjacent OSISs in the second tier network T2 throughthe corresponding optical paths. One of the N transmission modules ofone OADS 200 may be coupled to, through the corresponding optical paths,the corresponding transmission modules of adjacent OADSs in the sameoptical node pod in the first tier network T1, in which the number N isa positive integer greater than or equal to two.

In summary, the two methods of the pod incremental structure design inthe first tier network T1, by connecting in series the correspondingindependent transmission modules in the nodes of the required OADS 200with optical fiber to form a ring-shaped network structure, thus reducethe wiring complexity of system structure upgrade.

Further, as described in the previous paragraph, the same wavelength canbe reused in the first tier network T1. This is the wavelengthreusability feature in the first tier network T1. Specifically,wavelength reusability features are represented in two aspects of thenetwork structure. First, a plurality of independent transmission ringRing1 and Ring2 of each Pod may use the same wavelength combinationrepeatedly. Second, the intra-Pod optical signals of different pods canreuse the same wavelength combination repeatedly.

Every transmission ring in the same pod can use the optical signals withthe same wavelength (i.e., λ1) repeatedly to perform transmission. Indifferent pods, optical signals with the same wavelength (i.e., λ1) canbe reused without conflict.

Through the design of the above network structure, a large number ofinter-rack data transmission can be supported by using only a fewwavelength types. Meanwhile, the restriction on that each type ofwavelength in the optical fiber of the intelligence-defined opticaltunnel network system 100 can be configured to transmit a correspondingoptical signal to pass, and the upper limit (i.e., 40 kinds ofwavelength) of the type of wavelength which can be used in whole networksystem can be conquered.

Please refer to FIG. 3D. FIG. 3D is a schematic diagram of intra-Podsand the orientation of the optical signal in the pod in accordance withsome embodiments of the present disclosure. In the following paragraph,the required setting of the wavelength selective switch in the OADSs 200a-200 e for building intra-Pod optical tunnels and the orientation ofthe optical signals will be described according to FIG. 3D.

As shown in FIG. 3D and FIG. 2, the unit corresponding to the OADS 200 awould like to use the first transmission module 210 to transmit data tothe unit corresponding to the OADS 200 b in same pod P1 and the unitcorresponding to the OADS 200 c. In order to transmit two portions ofinformation respectively, the software-defined network controller 500can be configured to build two intra-Pod optical tunnels. One uses theroute RT1 from the OADS 200 a to the OADS 200 b and selects to usewavelength λ1. The other uses the route RT2 from the OADS 200 a to theOADS 200 c and selects to use wavelength λ2. For building the opticaltunnels, the wavelength selective switches on the route which should beset to select a specific wavelength to pass. Thus, the route RT1 onlyhas to set the 2×1 first wavelength selective switch (as the firstwavelength selective switch WSS11 shown in FIG. 2) in the firsttransmission module 210 of the OADS 200 b at the destination and theoptical tunnels can be built. The route RT2 has to set the 1×1 secondwavelength selective switch (as the second wavelength selective switchWSS12 shown in FIG. 2) at West-East orientation in the firsttransmission module 210 of the OADS 200 b and the 2×1 first wavelengthselective switch (as the first wavelength selective switch WSS11 shownin FIG. 2) in the first transmission module 210 of the OADS 200 c at thedestination.

In the process of optical signal transmission, first, the opticalsignals with the wavelength λ1 and the wavelength λ2 are transmitted to,through the corresponding DWDM transceiver on the input-output port ofthe ToR switches of the corresponding racks, the corresponding add-portof the first transmission module 210 a of the OADS 200 a, combined to anoptical fiber by the multiplexer 212, and are duplicated, split andtransmitted to the West through the 2×2 first splitter SP11. At thistime, the optical signals will be transmitted, the optical power beingamplified by the optical signal amplifier EDFA1, through the firsttransmission ring Ring1 to the first transmission module 210 b of theOADS 200 b. After the optical signals are transmitted to the firsttransmission module 210 b, the optical signal with wavelength λ1 and thewavelength λ2 will be duplicated and split into two optical signals bythe second splitter SP12. One optical signal is transmitted downwardly.The other optical signal is transmitted to the West to the OADS 200 c.Among them, the optical signal transmitted downwardly will pass throughthe 2×1 first wavelength selective switch WSS11 which selects theoptical signal with wavelength λ1 to pass and transmits to thedemultiplexer 216, and finally be transmitted to, through the firstdrop-port of the demultiplexer 216, the receiver of the correspondingDWDM transceiver on the input-output port of the ToR switch of thecorresponding rack. The optical transmission from rack to rack iscompleted.

On the other hand, the optical signal transmitted to the West will passthrough the 1×1 second wavelength selective switch WSS12 which selectsthe optical signal with wavelength λ2 to pass, and is duplicated, splitand transmitted to the West through the 2×2 first splitter SP11. At thistime, the optical signals will be transmitted, the optical power beingamplified by the optical signal amplifier EDFA1, through the firsttransmission ring Ring1 to the first transmission module 210 c of theOADS 200 c. After the optical signals are transmitted to the firsttransmission module 210 c, the optical signal with wavelength λ2 will beduplicated and split into two optical signals by the 1×2 second splitterSP12. One optical signal is transmitted downwardly. The other opticalsignal is transmitted to the West. The optical signal transmitteddownwardly will pass through the 2×1 first wavelength selective switchWSS11 which selects the optical signal with wavelength λ2 to pass andtransmits to the demultiplexer 216, and be transmitted to, through thesecond drop-port of the demultiplexer 216, the receiver of thecorresponding DWDM transceiver on the input-output port of the ToRswitch of the corresponding rack. The optical transmission from rack torack is completed.

In addition, the software-defined network controller 500 can beconfigured to set a 1×1 second wavelength selective switch in the firsttransmission module 210 c (refer to the second wavelength selectiveswitch WSS12 in FIG. 2) to filter and block the optical signal with thewavelength λ2 transmitted to the West in order to prevent the opticalsignal with the wavelength λ2 from continuing to be transmitted to thenext OADS 200 d.

Through this, it is possible to build different optical tunnels on thesame transmission ring Ring1 by using different wavelengths to transmitdata to different optical nodes respectively. Thus, in the first tiernetwork T1, the data transmission between the servers on different rackscorresponding to each one of the OADSs 200 a-200 e in the same pod canbe implemented.

Please refer to FIG. 1 again. As previously shown in FIG. 1, the firsttier network T1 includes a plurality of pods P1-P4. The pods P1-P4 viabeing interconnected to the second tier network T2 can be formed anetwork structure with larger scale.

Structurally, any one of the OSISs (i.e., the OSIS 400 a) of the secondtier network T2 is connected to two adjacent pods in the first tiernetwork T1 at the same time (i.e., Pod P1 and Pod P2). Thereby, datatransmission between servers corresponding to different pods can beimplemented through the OSISs 400 a-400 e in the second tier network T2.

Specifically, the first transmission modules 210 of the OADSs 200 a-200e in the pod P1 are coupled to the OSIS 400 a through a plurality offirst longitudinal ports respectively. The second transmission modules220 of the OADSs 200 a-200 e are coupled to, through a plurality ofsecond longitudinal ports to the OSIS 400 e respectively. In addition,the second transmission modules 220 in the pod P2 are coupled to theOSIS 400 a through a plurality of second longitudinal portsrespectively.

Alternately, any one of the OSISs 400 a-400 e in the second tier networkT2 is connected to the first transmission module 210 and the secondtransmission module 220 corresponding to different transmission rings ofthe OADSs 200 a-200 e in two adjacent pods in the first tier network T1.The OADSs 200 a-200 e in the same pod in any one of the first tiernetworks T1 are coupled to the adjacent two of the OSISs 400 a-400 e inthe second tier network T2 at the same time. through the dissimilarfirst transmission module 210 and the second transmission module 220.

As such, accompanied with the interconnect network between the OSISs 400a-400 e, any OADSs 200 a-200 e can be built a plurality of end-to-endoptical tunnels between each pod of the first tier network T1. Furtherthrough one or more OSIS 400 a-400 e, each pod of the first tier networkT1 is connected to OADSs 200 a-200 e of the other pods for transmission.

For ease of description, the following paragraphs are the descriptionwith the relevant diagrams for the internal specific structure of theOSIS 400 a and the relevant operation of an implement of optical signaltransmission. Please refer to FIG. 4. FIG. 4 is a schematic diagram ofan optical switch interconnect sub-system 400 a in accordance with someembodiments of the present disclosure. It should be noticed thatalthough FIG. 4 illustrates the structure and operation of the OSIS 400a as an example, the structures and operations of the remaining OSISs400 b-400 e are similar, and therefore will not be described again.

The OSIS 400 a is mainly used as a relay node for building opticaltunnels between different pods. As shown in FIG. 4, the internal designof the OSIS 400 a can be divided into a receiving sub-module 420, anoutput sub-module 440, an optical switching sub-module 460, and aninterconnection fabric module 480. The interconnection fabric module 480further includes a failover sub-module 490.

The OSIS 400 a includes a plurality of add-ports and drop-ports. Theamounts of them are equal and corresponsive to the amounts of the OADS200 in each pod in the first tier network T1. For example, when each podincludes five OADSs 200 a-200 e respectively, the OSIS 400 a should beconnected to ten OADSs in adjacent pod P1 and P2. Thus, ten add-portsand ten drop-ports are needed.

As shown in the figure, the receiving sub-module 420, coupled to eachadd-port, is configured to receive a plurality of first uplinktransmission optical signals TSu1 a-TSu1 e from a plurality of firstOADSs 200 a-200 e corresponding to the first pod P1 of the OSIS 400 a,and a plurality of third uplink transmission optical signals TSu3 a-TSu3e from a plurality of second OADSs 200 a-200 e corresponding to thesecond pod P2.

The OSIS 400 a respectively is connected to all the OADSs 200 a-200 e inthe two adjacent pods P1 and P2 in the first tier network T1 withoptical fibers. In order to combine and filter the optical signalsuploaded from the OADSs 200 a-200 e, in some embodiments, the receivingsub-module 420, including two wavelength band multiplexers (band MUX)BMUX1 and BMUX2, is configured to receive, respectively, the firstuplink transmission optical signals TSu1 a-TSu1 e, the third uplinktransmission optical signals TSu3 a-TSu3 e with different wavelengthbands transmitted by the OADSs 200 a-200 e in the pods P1 and P2, andcombine them into the composite signal SigU1 and SigU2 to one opticalfiber to enter into the optical switching sub-module 460.

In some embodiments, the two wavelength band multiplexers BMUX1 andBMUX2 are connected to different transmission rings of the OADSs ofdifferent pods P1 and P2. For example, as shown in FIG. 1 and FIG. 4,the wavelength band multiplexer BMUX1 is connected downwardly to thefirst transmission module 210 of each of the OADSs 200 a-200 e in thepod P1. The wavelength band multiplexer BMUX2 is connected downwardly tothe second transmission module 220 of each of the OADSs 200 a-200 e inthe pod P2. For ease of understanding, the connection between the firsttier network T1 and the second tier network T2 will be described indetail in the following paragraphs.

Therefore, in the embodiment shown in FIG. 1, if a pod P1 includes atmost five OADSs 200 a-200 e and the first transmission module 210 andthe second transmission module 220 of corresponding OADSs 200 a-200 e oneach transmission ring use different wavelength frequency bands, thewavelength band multiplexers BMUX1 and BMUX2 configured in the OSIS 400a are five-band multiplexer separately to allow the optical signals withfive different wavelength frequency band to pass through five add-ports,respectively. For example, for the optical signals entering into thewavelength band multiplexers BMUX1 through the first add-port, only theoptical signals with wavelength λ1-λ8 can pass, and the optical signalswith remaining wavelength are filtered out by the wavelength bandmultiplexers BMUX1. For the optical signals entering into the wavelengthband multiplexers BMUX1 through the second add-port, only the opticalsignals with wavelength λ9-λ16 can pass, and so on.

The output sub-module 440, coupled to each drop-port, is configured totransmit the composite optical signals SigD1 and SigD2 transmitted fromthe optical switching sub-module 460 to the pod P1 and P2 in the firsttier network T1. Specifically, the output sub-module 440 mainly includessplitters SPLT1 and SPLT2. In structure, the splitter SPLT1 is connectedto the OADSs 200 a-200 e in pod P1. The splitter SPLT2 is connected tothe OADSs 200 a-200 e in pod P2. The splitter SPLT1 and SPLT2 areconfigured to duplicate and split the composite optical signal SigD1 andSigD2 transmitted downwardly by the optical switching sub-module 460 asthe second downlink transmission optical signals TSd2 a-TSD2 e and thefourth downlink transmission optical signals TSd4 a-TSD4 e to each OADSs200 a-200 e of the pod P1 and P2 in the first tier network T1.

Therefore, in the embodiment shown in FIG. 1, if a pod P1 includes atmost five OADSs 200 a-200 e, the 1×5 splitter SPLT1 duplicates thecomposted optical signal SigD1 into five the second downlinktransmission optical signal TSd2 a-TSd2 e and outputs, to the firsttransmission module 210 of the five OADSs 200 a-200 e in the pod P1,respectively. The other 1×5 splitter SPLT2 duplicates the compostedoptical signal SigD2 into five the fourth downlink transmission opticalsignal TSd4 a-TSd4 e and outputs, to the second transmission module 220of the five OADSs 200 a-200 e in the pod P2, respectively.

In structure, the optical switching sub-module 460, coupled to thereceiving sub-module 420, the output sub-module 440 and theinterconnection fabric module 480, is configured to receive the opticalsignals transmitted between the sub-module 420, the output sub-module440 and the interconnection fabric modules 480.

In some embodiments, the optical switching sub-module 460 includes anN×M wavelength selective switch for wavelength selection, so that theOSIS 400 a can transmit the optical signals which are transmitted fromthe first tier network T1 to the East and the West to other OSISs (suchas OSISs 400 b-400 e) or downwardly to other pods in the first tiernetwork T1, and can also receive optical signals from other OSISs 400b-400 e in East and West direction and transmit them to the pod P1 andP2 in the first tier network T1. N and M are any positive integersgreater than or equal to two and depend on the amount of transmissionmodules included in one OADS 200 and the amount of the OSISs 400 a-400 eincluded in the second tier network T2, in which the OSISs 400 a-400 eare connected to each other.

Taking the embodiment shown in FIG. 1 as an example, since one OADS 200includes two independent first transmission modules 210 and secondtransmission modules 220, the OSIS 400 a is configured with two pods ofmultiplexer BMUX1, BMUX2. Correspondingly, the optical switchingsub-module 460 includes a first uplink input terminal and a seconduplink input terminal, which are, respectively coupled to themultiplexer BMUX1 and the multiplexer BMUX2, configured to receive acomposite optical signal SigU1 and a composite optical signal SigU2,respectively.

In addition, since there are five OSISs 400 a-400 e connected in thesecond tier network T2, each OSIS (such as the OSIS 400 a) has fourlines connected from the other four OSIS 400 b-400 e. Therefore, theoptical switching sub-module 460 includes a plurality of correspondingdownlink input terminals coupled to the interconnection fabric module480 and configured to receive the lateral transmission optical signalstransmitted by the remaining OSISs 400 b-400 e. Thus, in thisembodiment, the amount of input terminals of the optical switchingsub-module 460 is two uplink input terminals plus four downlink inputterminals, and the value of N is six.

On the other hand, since the OSIS 400 a is configured to transmit datadownwardly to two pods P1, P2, the OSISs 400 a is configured with twosplitters SPLT1, SPLT2. Correspondingly, the optical switchingsub-module 460 includes a first downlink output terminal and a seconddownlink output terminal, which are respectively coupled to the splitterSPLT1 and the splitter SPLT2. The splitter SPLT1 is configured to outputthe second downlink transmitted optical signal TSd2 a-TSd2 e. Thesplitter SPLT2 is configured to output the fourth downlink transmissionoptical signals TSd4 a-TSd4 e.

In addition, the OSIS 400 a is further configured to output signals inEast and West direction to the remaining OSIS 400 b-400 e. Therefore,the optical switching sub-module 460 includes a first uplink outputterminal and a second uplink output terminal, which are, respectivelycoupled to the interconnection fabric module 480, configured to outputthe lateral transmission optical signal to the remaining OSISs 400 b-400e. As a result, in this embodiment, a total of four outputs arerequired, and the value of M is 4.

In this structure, the 6×4 (6 in and 4 out) optical switching sub-module460 simplifies the fabric design compared to the existing opticalswitching sub-module. Not only is the usage of line less, but also theoptical switching sub-module 460 can be configured to be used with thefailover sub-module for detecting the intensity of optical signals(please refer to FIG. 6).

Please refer to FIG. 5. FIG. 5 is a schematic diagram of the internaldesign of the optical switching sub-module 460 in accordance with someembodiments of the present disclosure. As shown in FIG. 5, the 6×4optical switching sub-module 460 includes a plurality of input splitters462 a-462 f, a wavelength selective switch array 464, a plurality ofoutput combiners 466 a-466 d, and a plurality of optical signalamplifiers 468 a-468 d. Precisely, in the optical switching sub-module460, the amount of input splitters 462 a-462 f corresponds to the Npieces of input terminals, the number of output combiners 466 a-466 dand the optical signal amplifiers 468 a-468 d correspond to the numberof output terminals M. In this embodiment, the 6×4 optical switchingsub-module 460 includes six input splitters 462 a-462 f, four outputcombiner 466 a-466 d, and four optical signal amplifiers 468 a-468 d.The wavelength selective switch array 464 is an array combined withfourteen 1×1 wavelength selective switches 464 a-464 n. In thisembodiment, the six input splitters 462 a-462 f include four downlinktransmission input splitters 462 a-462 d and two uplink transmissioninput splitters 462 e-462 f. The fourteen wavelength selective switches464 a-464 n include four laterally transmission wavelength selectiveswitches 464 a-464 d, the downlink transmission wavelength selectiveswitches 464 e-464 i in the first part, and the downlink transmissionwavelength selective switches 464 j-464 n in the second part. Fouroutput optical combiners 466 a-466 d include two lateral transmissionoutput combiners 466 a-466 b and two downlink transmission outputcombiner 466 c-466 d.

In operation, the input splitters 462 a-462 f, coupled to the downlinkinput terminal, the first uplink input terminal, or the second uplinkinput terminal respectively, are configured to duplicate andcorrespondingly output a plurality of first optical signals to aplurality of wavelength selective switches 464 a-464 n in the wavelengthselective switch array 464. The wavelength selective switches 464 a-464n are respectively configured to receive and select, according to acontrol signal CS outputted by the software-defined network controller500, the corresponding wavelength of the first optical signal as thesecond optical signal to the corresponding output combiners 466 a-466 d.The output combiners 466 a-466 d are respectively configured to receiveand combine two or more of the second optical signals to output aplurality of third optical signals to the optical signal amplifiers 468a-468 d. Thereby, the optical signal amplifiers 468 a-468 d can amplifythe third optical signal and output the amplified third optical signalas composite optical signal SigD1, SigD2, SigE0 and SigW0 through thefirst downlink output terminal, the second downlink output terminal, thefirst uplink output terminal or the second uplink output terminalrespectively. The following paragraphs describe the operation of eachdevice unit separately.

Specifically, the uplink transmission input splitter 462 e is coupled tothe first uplink input terminal, and the uplink transmission inputsplitter 462 f, coupled to the second uplink input terminal, isconfigured to receive the composite signal SigU1 and SigU2 from themultiplexer BMUX1 and the multiplexer BMUX2. The uplink transmissioninput splitter 462 e and the uplink transmission input splitter 462 fare configured to duplicate and split the composite signal SigU1 andSigU2 into three beams and be connected to the three different 1×1wavelength selective switches 464 a-464 n in the wavelength selectiveswitch array 464, respectively. As shown in the figure, the uplinktransmission input splitter 462 e is coupled to the wavelength selectiveswitches 464 a, 464 c, 464 n, and correspondingly outputs a firstlateral transmission signal H1E, a second lateral transmission signalH1W and the third downlink transmission signal U1D2. The uplinktransmission input splitter 462 f is coupled to the wavelength selectiveswitches 464 b, 464 d, 464 i, and correspondingly outputs a firstlateral transmission signal H2E, a second lateral transmission signalH2W and the third downlink transmission signal U2D1.

The downlink input terminals are configured to receive optical signalsfrom each two OSIS at the East and the West respectively. For example,for the optical switching sub-module 460 in the OSIS 400 a, the downlinkinput terminals are configured to receive the lateral optical signalsSigE1 and SigE2 transmitted from the optical switching sub-module 460 band 460 c at the East and the lateral optical signals SigW1 and SigW2transmitted from the optical switching sub-module 460 e and 460 d at theWest. The optical signal SigE1, SigE2, SigW1, and SigW2 are respectivelytransmitted to the 1×2 downlink transmission input splitters 462 a, 462b, 462 c, 462 d through the downlink input terminal with the opticalfiber connection in order to be duplicated and split into two beams andconnected to the corresponding one of the 1×1 wavelength selectiveswitches 464 a-464 n.

Specifically, any one of the downlink transmission input splitters 462a-462 d coupled to the corresponding one of the downlink input terminal,is configured to duplicate the lateral optical signal SigE1, SigE2,SigW1, and SigW2 received from the corresponding OSIS 400 b-400 e andoutputted the corresponding first downlink transmission signal E1D1,E2D1, W1D1, W2D1 and the second downlink transmission signal E1D2, E2D2,W1D2 and W2D2 to the corresponding one of the wavelength selectiveswitches 464 a-464 n in the wavelength selective switch array 464.

As shown in the figure, in an embodiment, the downlink transmissioninput splitter 462 a is connected to and outputs the first downlinktransmission signal E1D1 and the second downlink transmission signalE1D2 to the corresponding wavelength selective switches 464 e, 464 j.The downlink transmission input splitter 462 b is connected and outputsthe first downlink transmission signal E2D1 and the second downlinktransmission signal E2D2 to the corresponding wavelength selectiveswitches 464 f, 464 k. The downlink transmission input splitter 462 c isconnected and outputs the first downlink transmission signal W1 D1 andthe second downlink transmission signal W1D2 to the correspondingwavelength selective switches 464 g, 464 l. The downlink transmissioninput splitter 462 d is connected and outputs a first downlinktransmission signal W2D1 and a second downlink signal W2D2 to thecorresponding wavelength selective switches 464 h, 464 m.

In the fourteen wavelength selective switches 464 a-464 n in thewavelength selective switch array 464, among them, four lateraltransmission wavelength selective switches 464 a, 464 b, 464 c, 464 dare configured to, respectively, perform wavelength selection to thelateral transmission signal H1E, H2E, H1W, and H2W transmitted to theother optical switching sub-module 460 in East and West direction in thesecond tier network T2 in order to select the corresponding wavelengthto be output as the third optical signal. The downlink transmissionwavelength selective switches 464 e-464 i in the first part and thedownlink transmission wavelength selective switches 464 j-464 n in thesecond part are configured to perform wavelength selection to thedownlink transmission signals transmitted downwardly in the adjacentpods in the first tier network T1.

Specifically, the downlink transmission wavelength selective switches464 e-464 i in the first part are configured to, respectively, selectthe downlink transmission signal E1D1, E2D1, W1D1, W2D1 and thecorresponding wavelength of the downlink transmission signal U2D1 andoutput as the corresponding third optical signal. The downlinktransmission wavelength selective switches 464 j-464 n in the secondpart are configured to, respectively, select the downlink transmissionsignal E1D2, E2D2, W1D2, W2D2 and the corresponding wavelength of thedownlink transmission signal U1D2 and output as the corresponding thirdoptical signal. Thus, the downlink transmission wavelength selectiveswitches 464 e-464 i in the first part can perform wavelength selectionto the optical signal transmitted to the pod P1 downwardly. The downlinktransmission wavelength selective switches 464 j-464 n in the secondpart can perform wavelength selection to the optical signal transmittedto the pod P2 downwardly.

In summary, after the operation of the wavelength selection is completedby the fourteen wavelength selection switches 464 a-464 n in thewavelength selective switch array 464, the third optical signalsoutputted by the wavelength selective switch array 464 have fourtransmission direction, to East, to West, to the pod P1 and the pod P2respectively. Each wavelength selective switch 464 a-464 n with sametransmission direction are connected to the corresponding one of theoutput combiner 466 a-466 d to combine the optical signals into oneoptical path.

As shown in the embodiment in FIG. 5, the lateral transmission outputcombiner 466 a is configured to combine the third optical signals outputfrom the lateral transmission wavelength selective switch 464 a and 464b. The other lateral transmission output combiner 466 b is configured tocombine the third optical signals output from the lateral transmissionwavelength selective switch 464 c and 464 d. The downlink transmissionoutput combiner 466 c is configured to combine the third optical signalsoutput from the downlink transmission wavelength selective switches 464e-464 i in the first part. The downlink transmission output combiner 466d is configured to combine the third optical signals output from thedownlink transmission wavelength selective switches 464 j-464 n in thesecond part.

Finally, the output combiner 466 a-466 d are respectively connected tothe corresponding one of optical signal amplifiers 468 a-468 d in orderto enhance optical signal intensity to ensure that the composite opticalsignal SigD1, SigD2, SigE0 and SigW0 have sufficient power to betransmitted to the destination.

It should be noticed that similar to the optical communication in thefirst tier network T1, when the optical signals with the same wavelengthenter into the optical switching sub-module 460 at the same time, theconflict may be caused by the optical signals with the same wavelengthpassing through the same output combiner 466 a-466 d.

For example, when the optical signals SigU1 and SigU2 from the pod P1and the pod P2 are both transmitted to the East if wavelengths of bothsignals are λ5, the two optical signals with wavelength λ5 are combinedinto one optical fiber through the output combiner 466 a and conflictoccurs. Similarly, if the optical signal SigU1 and SigU2 are bothtransmitted to the West, the conflict occurs by the output combiner 466b. Furthermore, when the wavelengths of the two optical signal sigE1 andSigW1 from the first OSIS 400 b and 400 e at the East and the West areboth wavelength λ6, the composite optical signal passing to the pod P1through the 5×1 output combiner 466 c will cause conflict. Similarly, ifthe optical signal is transmitted to the pod P2, the conflict occurs bythe 5×1 (5 input and 1 output) output combiner 466 d.

Please refer to FIG. 6. FIG. 6 is a schematic diagram of theinterconnection fabric module 480 in accordance with some embodiments ofthe present disclosure. The interconnection fabric module 480 isconfigured to connect the OSISs 400 a-400 e. Any two of the OSISs 400a-400 e transmit the corresponding lateral transmission optical signalbetween each other through the corresponding first line (i.e., thenormal fabric). In some embodiments, any two of the OSISs 400 a-400 eare connected to each other with the second line (i.e., the protectionfabric) which is different from the first line. The interconnectionfabric module 480 includes the failover sub-module 490.

Specifically, The interconnection fabric module 480 includes uploadterminal In1, In2, East output terminal E1, E2, East protection outputterminal E3-E6, East input terminal E7-E8, East protection inputterminal E9-E12, West input terminal W1, W2, West protection inputterminal W3-W6, West output terminal W7, W8, West protection outputterminal W9-W12, interconnect splitters 481-486 and the failoversub-module 490.

The interconnection fabric module 480 includes the internal fabrics forthe OSIS 400 a to connect to the other OSISs 400 b-400 e in East andWest direction. As shown in the figure, the interconnect fabrics includethe normal fabric and the protection fabric. The normal fabric (as shownwith the solid line) is configured to transmit the optical signals underthe normal condition of the system. The protection fabric (as shown withthe dash line) is configured to transmit the optical signals in reversedirection under the condition of the normal fabric being cut off. Theamount of interconnect circuits depends on the total amount of OSISs 400a-400 e to which the system is connected. For example, the presentembodiment is a fabric diagram of the interconnect situation of fiveOSISs 400 a-400 e. In fact, the interconnect structure between the OSISs400 a-400 e in the second tier network T2 is essentially a meshstructure. Thus, there will be one output line NLE0 to the East, oneoutput line NLW0 to the West, two input line NLE1, NLE2 from the OSIS(i.e., OSIS 400 b and OSIS 400 c) from the East, two input line NLW1,NLW2 from the OSIS (i.e., OSIS 400 e and OSIS 400 d) from the West.There are a total of two normal solid lines connected to the OSIS 460and a total of four normal solid lines connected to the failoversub-module 490.

On the other hand, there will be at least six protection output linePLW0, PLE0 and protection input line PLE1, PLE2, PLW1, PLW2 (dash line)because of one-to-one correspondence with the normal lines. Theremaining lines are transition lines. Some lines utilize interconnectsplitters 481-486 to duplicate and split the optical signals andtransmits to the OSIS and next OSIS at the same time. The other transitthis OSIS directly and are connected to the next OSIS in East-Westdirection.

The input lines NLE1, NLE2, NLW1, NLW2 and the protection input linesPLE1, PLE2, PLW1, and PLW2 are coupled to the failover sub-module 490.As the embodiment shown in FIG. 6, the input lines NLE1, NLE2, NLW1,NLW2 and the protection input lines PLE1, PLE2, PLW1, and PLW2 aredirectly connected to the failover sub-module 490. However, the presentdisclosure is not limited therein. In other embodiments, the input linesNLE1, NLE2, NLW1, NLW2 and the protection input lines PLE1, PLE2, PLW1,and PLW2 can be connected to the failover sub-module 490 indirectly. Onthe other hand, the output lines NLE0 and NLW0 are connected to theoptical switching sub-module 460.

For the signals to be output from the pod P1 or the pod P2 to the otherOSISs 400 b-400 e, firstly, from the optical switching sub-module 460,two optical fibers from the OSIS to the East and the West will beconnected to the first upload terminal In1 and the second uploadterminal In2 of the interconnection fabric module 480 respectively.

The first upload terminal In1 and the second upload terminal In2 areconnected to a 1×2 interconnect splitter 485 and 486. The interconnectsplitter 485 is configured to duplicate and output the composite opticalsignal SigW0 received from the optical switching sub-module 460 as alateral transmission optical signal SigW7 through the first West outputterminal W7 (i.e., line NLW0) and as another lateral transmissionoptical signal through the first East protection terminal E3 (i.e., linePLE0). Similarly, The interconnect splitter 486 is configured toduplicate and output the composite optical signal SigE0 received fromthe optical switching sub-module 460, through the first East outputterminal E1 (i.e., line NLE0) as a lateral transmission optical signalSigE1 and through the first West protection output terminal W9 (i.e.,line PLW0) as a lateral transmission optical signal SigW9.

In other words, the interconnect splitters 485 and 486 are configured toduplicate and split the optical signal into two beams, respectively, onebeing transmitted in the normal direction (which are the normal fabricNLW0 and NLE0) to the OSISs 400 e, 400 d, 400 b and 400 c, the otherbeing transmitted in reverse direction (which are the protection inputlines PLE0 and PLW0).

As shown in the figure, the interconnection fabric module 480 transmitsthe corresponding lateral transmission optical signal SigE1 to the OSISs400 b and 400 c in a first direction (i.e., eastward) and thecorresponding lateral transmission optical signal SigW7 to the OSISs 400e and 400 d in a second direction (i.e., westward) which is differentwith the first direction. In other words, in the normal path, theinterconnection fabric module 480 transmits the optical signals to theremaining OSIS 400 b-400 e in two different directions.

Similarly, for the signals received from the other OSISs 400 b-400 e andoutput to the pod P1 or the pod P2, there are the normal fabric and theprotection fabric separately. In the aspect of the normal fabric, thenormal fabrics NLE1 and NLW1, connected through two input ports, a firstEast input PiE1 and a first West input PiW1, are configured to receivesignals from the first OSIS 400 b at the East and the first OSIS 400 eat the West.

The first east input terminal E7 and the first west input terminal W1receive, respectively, the lateral transmission optical signals SigW7′and SigE1′ from the first west output terminal W7 and first East outputterminal E1 of the interconnection fabric module 480 of the adjacentOSISs 400 b and 400 e. On the normal fabric, the normal fabrics NLE1 andNLW1 are connected to a interconnect splitters 482 and 481 respectivelyto duplicate and split the lateral transmission optical signals SigW7′and SigE1′ into two beams, one being transmitted continually westwardand eastward, the other being transmitted to the local failoversub-module 490.

As shown in the figure, the two lines eastward and westward are finallyconnected to the position of the output port shifted downwardly. Inother words, the interconnect splitter 481 is configured to duplicate alateral transmission optical signal SigE1′ received from the first westinput terminal W1 and output it as a lateral transmission optical signalSigE2 through the second east output terminal E2. The interconnectsplitter 482 is configured to duplicate a lateral transmission opticalsignal SigW7′ received from the second west input terminal W8 and outputit as a lateral transmission optical signal SigW8 through the secondwest output terminal W8. In addition, the two lines transmitting to thelocal failover sub-module 490 are connected to output ports O4 and O8respectively.

The second pod of normal fabrics NLE2, NLW2, connected from, the secondeast input terminal E8 and a second west input terminal W2 respectively,are configured to receive the lateral transmission optical signalsSigW8′ and SigE2′ transmitted from the second OSIS 400 c at the east andthe second OSIS 400 d at the west, connected to the output ports O3, O7respectively and are connected directly to the local failover sub-module490.

In the aspect of protection fabric, the basic design principle is toconfigure the fabric corresponding to the normal lines but in reversetransmission direction in order to be connected to the node of the OSISat the same destination of the normal (solid line) path.

Different with the normal fabric, under the condition of five OSISs 400a-400 e interconnected with each other, the protection path needs topass two nodes of the OSISs in reverse direction and then reaches thenode of the OSIS at the same destination of the normal path.

For example, assuming that the line of the present OSIS at the east iscut off, the optical signals of two OSISs at the east must betransmitted westward through the protection path (the two OSIS at thewest is not affected, using the original normal path). The opticalsignal must bypass two OSIS and then reach the two OSIS at the east. Itis not necessary for the system to receive the optical signal when theybypass the two OSIS at the west.

Thus, there is no splitter configured in every two optical fibers on theprotection path eastward and westward in the OSIS 400 a. As shown in thefigure, the first east protection input terminal E9 and the first westprotection input terminal W3 are configured to, respectively, receivethe lateral transmission optical signals from the first west protectionoutput terminal W9 and the first east protection output terminal E3 inthe interconnection fabric module 480 of the adjacent OSISs 400 b and400 e and output the lateral transmission optical signals through thesecond west protection output terminal W10 and the second eastprotection output terminal E4.

Similarly, the second east protection input terminal E10 and the secondwest protection input terminal W4 are configured to, respectively,receive the lateral transmission optical signals from the second westprotection output terminal W10 and the second east protection outputterminal E4 in the interconnection fabric module 480 of the adjacentOSISs 400 b and 400 e and output the lateral transmission opticalsignals through the third west protection output terminal W11 and thethird east protection output terminal E5.

The third east protection input terminal E11 and the third westprotection input terminal W5 are configured to, respectively, receivethe lateral transmission optical signals from the third west protectionoutput terminal W11 and the third east protection output terminal E5 inthe interconnection fabric module 480 of the adjacent OSISs 400 b and400 e.

The interconnect splitters 484 and 483, coupled to the third eastprotection input terminal E11 and the third west protection inputterminal W5, are configured to duplicate the received lateraltransmission optical signals, be connect to the position of the outputport shifted downwardly, transmit optical signals through the fourthwest protection output terminal W12 and the fourth east protectionoutput terminal E6 and output the lateral transmission optical signalsthrough the output terminals O2 and O6 to the failover sub-module 490.

Finally, the fourth east protection input terminal E12 and the fourthwest protection input terminal W6 are configured to, respectively,receive the lateral transmission optical signals from the fourth westprotection output terminal W12 and the fourth east protection outputterminal E6 in the interconnection fabric module 480 of the adjacentOSISs 400 b and 400 e and output the lateral transmission opticalsignals through the output terminals O1 and O5 to the failoversub-module 490.

As shown in the figure, the failover sub-module 490 is coupled to theinterconnect splitters 483, 484, the fourth east protection inputterminal E12 and the fourth west protection input terminal W6.Furthermore, the failover sub-module 490 is coupled to the interconnectsplitters 481, 482 on the normal path, the second east protection inputterminal E8 and the second west protection input terminal W2. In thisway, the failover sub-module 490 can be configured to receiveselectively the lateral transmission optical signal transmitted from thenormal path or the protection path. The failover sub-module 490 canoutput the lateral transmission optical signal to the optical switchingsub-module 460 from the normal path through interconnect splitters 481and 482, the second east input terminal E8 and the second west inputterminal W2 or selectively output the lateral transmission opticalsignal to the optical switching sub-module 460 from the protection paththrough interconnect splitters 483 and 484, the fourth east protectioninput terminal E12 and the fourth west protection input terminal W6.

As shown in the figure, the failover sub-module 490 includes a pluralityof optical switches 492, 494, 496, and 498. The optical switches 492,494, 496, and 498 receive, through the first line (which is the normalfabric) and the second line (which is the protection fabric), the firstlateral transmission optical signal (transmitted via the normal fabric)and the second lateral transmission optical signal (transmitted via theprotection fabric) from the corresponding one of the remaining OSISs 400b-400 e. The first lateral transmission optical signal and the secondlateral transmission optical signal here refer to the lateraltransmission optical signal transmitted between different OSISs 400a-400 e in the ring-shaped mesh structure R2. One of the first lateraltransmission optical signal and the second lateral transmission opticalsignal is outputted to the optical switching sub-module 460,corresponding to a select signal SS output from the micro-control unit410 (MCU). Transmitting lateral optical signals in the ring-shaped meshstructure R2 will be further described in the following embodiment.

Please refer to FIG. 7A and FIG. 7B. FIG. 7A is a schematic diagram ofan interconnection network between the OSISs 400 a-400 e in a secondtier network T2 in accordance with some embodiments of the presentdisclosure. FIG. 7B is a partially enlarged schematic view of FIG. 7A.

The interconnection network is mainly configured to build the opticaltunnel for transmission between the OSIS 400 a-400 e, such that each podin the first tier network T1 to which each OSISs 400 a-400 e isconnected can transmit optical signals to each other. As mentionedabove, the interconnection network between the OSISs 400 a-400 e isessentially in a mesh structure. Through some optical fibers in theRibbon fiber, the connections from every OSISs 400 a-400 e to other OSISare independent of each other. For example, the connection between theOSIS 400 a and the other OSIS 400 b-400 e and the connection between theOSIS 400 b and the other OSIS 400 a, 400 c-400 e are independent of eachother.

Since the ribbon fiber is adopted, all the OSISs 400 a-400 e areconnected in a ring structure in appearance, which simplifies the wiringcomplexity. In addition, because of this mesh network architecture, datatransmission between pairs of different OSISs 400 a-400 e can besimultaneously transmitted using the same wavelength combination withoutconflict, highlighting the characteristics of wavelength reusability.

Please refer to FIG. 4 and FIG. 6 for a better understanding of theinterconnect network between OSISs 400 a-400 e illustrated in FIG. 7Aand FIG. 7B.

As shown in FIG. 7A, under normal circumstances, the 400 a will transmitand receive optical signals from the normal path to/from the OSISs 400b, 400 c at the two nodes in the east and to/from the OSISs 400 d, 400 eat the two nodes in the west. Accompanied by the design of the internalinterconnection fabric module 480 shown in FIG. 6, when the OSISs 400a-400 e are interconnected via optical fibers, the optical paths of theeast output terminals E1-E6 and the east input terminals E7-E12 theinterconnection fabric of OSIS 400 a are connected via optical fibersand correspond to the optical paths of the west input terminals W1-W6and the west output terminals W7-W12 in the interconnection fabric ofthe next OSIS 400 b, and so on.

Furthermore, since the factor of the interconnect structure between theOSISs 400 a-400 e, they can utilize the same wavelength combination (λ5,λ6, λ7, λ8) to transmit optical signals to each other without conflict,having the characteristics of wavelength reusability. As shown in thefigure, the OSIS 400 a can transmit optical signals to the OSISs 400b-400 e, respectively, in wavelength combinations λ5, λ6, λ7, and λ8.The OSIS 400 b can also transmit optical signals to the OSISs 400 c-400e, 400 a, respectively, in wavelength combinations λ5, λ6, λ7, λ8without causing conflicts. Similarly, the same wavelength combinationλ5, λ6, λ7 and λ8 may be reused for transmitting optical signals toother OSISs in other OSISs 400 c to 400 e, and the contents thereof arenot described herein.

In the example shown in FIG. 7A, the path RTa represents that theoptical signal SigA with the wavelength λ5 of the pod P2 in the firsttier network T1 is transmitted from the OSIS 400 a through the normalpath to a first node (the OSIS 400 b) at the east side. During thetransmission, the 6×4 wavelength selective switch (i.e., opticalswitching sub-module 460) of the OSIS 400 a selects the optical signalSigA from the pod P2 to be transmitted eastward, duplicated via the 1×2internal interconnect splitter 486, split and transmitted to the nextnode (the OSIS 400 b) in the normal direction (i.e., east). When theoptical signal SigA enters into the internal interconnect circuit of thedestination OSIS 400 b, the optical signal SigA is duplicated, split andtransmitted to the failover sub-module 490 of the OSIS 400 b via the 1×2interconnect splitter 481. At this time the failover sub-module 490passes the optical signals which are on the normal path and transmitsthem to the 6×4 wavelength selective switch (i.e., the optical switchingsub-module 460) of the OSIS 400 b for wavelength selection andreception. The specific details of transmission of the optical signalsare shown in FIG. 7B and will not be described here.

One the other hand, the path RTb represents that the optical signal SigBwith the wavelength λ7 of the pod P1 in the first tier network T1 istransmitted from the OSIS 400 a through the normal path to a second node(the OSIS 400 d) at the west side. During the transmission, the 6×4wavelength selective switch (i.e., optical switching sub-module 460) ofthe OSIS 400 a selects the optical signal SigB from the pod P1 to betransmitted westward, duplicated via the 1×2 internal interconnectsplitter 485, split and transmitted to the next node (the OSIS 400 e) inthe normal direction (i.e., west).

When the optical signal SigB enters into the internal interconnectfabric of the OSIS 400 e, the optical signal SigB is duplicated, splitand transmitted to the next node (OSIS 400 d) continuously via the 1×2internal interconnect splitter 482. When the optical signal SigB entersinto the internal interconnect circuit of the destination OSIS 400 d,the optical signal SigB is transmitted directly to the failoversub-module 490 of the OSIS 400 d. At this moment, the failoversub-module 490 passes the optical signals which are on the normal pathand transmits them to the 6×4 wavelength selective switch (i.e., theoptical switching sub-module 460) of the OSIS 400 d for wavelengthselection and reception.

Please refer to FIG. 8A. FIG. 8A is a schematic diagram of the operationof a protection fabric in accordance with some embodiments of thepresent disclosure. As shown in FIG. 8A, it is assumed that the ribbonfiber between the OSIS 400 a and the OSIS 400 e is disconnected, therebycausing the OSIS 400 a to be not able to transmit the optical signalSigC to the west through the normal path to the OSIS 400 e and theoptical signals to the OSIS 400 d. At this time the failover sub-module490 of the OSIS 400 e detects that the intensity of the light of thefirst OSIS at the east becomes weaker, thus automatically switches theconnection to the protection path RTc.

In fact, if the ribbon fiber between the OSISs 400 a and 400 e isdisconnected, it will also affect the signal transmission of otherOSISs.

In the present embodiment, the statuses of every OSISs 400 a-400 ereceiving the optical signals from other two OSISs at the east/west areshown as table 2 below.

TABLE 2 (Receiving optical signals statuses of the OSIS) optical signalFirst OSIS Second OSIS First OSIS Second OSIS receiving status at theeast at the east at the west at the west 400a ◯ ◯ X X 400b ◯ ◯ ◯ X 400c◯ ◯ ◯ ◯ 400d ◯ X ◯ ◯ 400e X X ◯ ◯

In Table 2, mark O represents that optical signals may be receivedthrough the normal path, and mark X represents that optical signals maynot be received through the normal path and it is necessary to, by thefailover sub-module 490, switch the connection to the protection path inorder to receive optical signals. Therefore, only OSIS 400 c is notaffected by the disconnection of the ribbon fibers. Some of receivingpaths of the other OSISs are affected by the disconnection of ribbonfiber, and it is needed to switch the connection to the protection pathsvia the failover sub-module 490.

In fact, under normal circumstances, the optical signal SigC will beduplicated into two beams through the interconnect splitter 485 of theOSIS 400 a and simultaneously sent to the normal path (i.e., the firstlateral transmission optical signal to the west) and the protection path(i.e., the path RTc to the east of the second lateral transmissionoptical signal). When the optical signal SigC is transmitted to the eastvia the protection path, it will transit two nodes (the OSISs 400 b and400 c) without passing through its internal interconnect splitters, andthen transmitted to the OSIS 400 d. When the optical signal SigC entersinto the internal interconnect circuit of the OSIS 400 d, it isduplicated, split to the east via the 1×2 interconnect splitter 483 andcontinuously transmitted to the next node (the OSIS 400 e).

Finally, when the optical signal SigC enters into the internalinterconnect circuit of the OSIS 400 e as the destination, it isdirectly transmitted to the failover sub-module 490 of the OSIS 400 e.At this time, the failover sub-module 490 switches the connection to theprotection path, so the optical signal SigC will pass through and betransmitted to the 6×4 wavelength selective switch (i.e., the opticalswitching sub-module 460) of the OSIS 400 e for wavelength selection andreception.

Accordingly, the optical switches 492, 494, 496 and 498 of the failoversub-module 490 in the OSIS 400 a can receive respectively, through thenormal fabric, the first lateral transmission optical signal from thecorresponding one of the other OSISs 400 b-400 e. By receiving thesecond lateral optical signal via the protection fabric, one of thefirst lateral transmission optical signal and the second lateraltransmission optical signal can be output, corresponding to theselective signal SS, to the optical switching sub-module 460. In thisway, when the normal fabric is disconnected, or other failures causesthe first lateral transmission optical signal disappeared, or intensitydecreased, the corresponding optical switches 492, 494, 496 and 498 canswitch to the protection path and perform signal transmission with thesecond lateral transmission optical signal.

Please refer to FIG. 6 again. As shown in FIG. 6, except the opticalswitches 492, 494, 496 and 498 in the failover sub-module 490, there arefour tap photodetectors (tap PD) 491, 493, 495 and 497 disposed in thefailover sub-module 490. As mentioned in the previous paragraphs, the2×1 optical switches 492, 494, 496 and 498 are configured to receive theoptical signals from the normal path (solid line) and the protectionpath (dash line) of each two OSISs in the east and the west,respectively.

As shown in the figure, the optical signals entering into the normalpath and the protection path of the same 2×1 optical switches 492, 494,496 and 498 are transmitted in the normal direction and reversedirection from the source terminal by being duplicated and split viautilizing the interconnect splitter 485 and 486. Thus, the data carriedby the two optical signals is the same. The default switch setting ofeach 2×1 optical switch 492, 494, 496 and 498 is to allow the opticalsignals in the normal path to pass.

In addition, in some embodiments, the function of the tap PDs 491, 493,495 and 497 is to convert around 2% of optical input power into thecorresponding current value and then through analog-to-digital converterconvert to the corresponding voltage value, such that the opticalswitches 492, 494, 496 and 498 can perform switch according to thevoltage value respectively.

For example, when the voltage value is lower than a threshold value(i.e., a wire disconnected or a poor signal is detected), amicro-control unit (MCU) 410 in the OSIS 400 a outputs signal SS toswitch the corresponding 2×1 optical switches 492, 494, 496 and 498 tochange to pass the optical signals of the protection path. Accordingly,the micro-control unit 410 can be configured to output the selectivesignal SS to the failover sub-module 490 in order to control thefailover sub-module 490 to output the second lateral transmissionoptical signal when the intensity of the first lateral transmissionoptical signal is lower than the threshold value.

Specifically, there are two different ways for the micro-control unit410 to determine when to activate the optical path switch. First, thefirst diagnostic mechanism for determining is a polling mechanism.Please refer to the FIG. 8B. FIG. 8B is a flow chart of thedetermination method 800 of the micro-control unit 410 in the pollingmechanism in accordance with some embodiments of the present disclosure.In the polling mechanism, the micro-control unit 410 can continuouslyand actively supervise the voltage status of each tap PD 491, 493, 495and 497. If the disconnection occurs, optical switches are performed tobe switched. In some embodiments, the micro-control unit 410 can executea driver program to perform the corresponding operation of thedetermination method 800.

As shown in FIG. 8B, the determination method 800 includes stepsS810-S840. First, in step S810, it is to utilize the driver program inthe micro-control unit 410 to read the voltage value of each tap PD 491,493, 495 and 497 sequentially. Moreover, in step S820, it is to comparethe voltage values read by the tap PDs 491, 493, 495 and 497 with thedefault threshold values respectively.

When the voltage values are larger than the threshold value, step 830 isperformed and steps S810-S830 are repeated with a time interval (i.e.,five seconds).

When the voltage values are less than the threshold value, step S840 isperformed to execute the unusual processing procedure. Step S840 furtherincludes steps S841-S845. First, in step S841, the number of times ofunusual status is determined based on the system record of the systemfirmware. In other words, the driver program can determine whether theunusual status was detected for the first time or the second time.

When it is the first time that the driver program detects the voltagevalue of one of the tap PDs 491, 493, 495 and 497 is less than thedefault threshold value, the corresponding normal receiving path can beregarded as a fault condition and the step S842 and step S843 areperformed. In the step S842, the micro-control unit 410 outputs theselective signal SS to switch the corresponding 2×1 optical switches492, 494, 496 and 498, such that the optical signals of the backupprotection path can pass. In S843, the micro-control unit 410 outputsthe unusual information signal to notify the system firmware that one ofthe tap PDs 491, 493, 495 and 497 occurs an unusual status for the firsttime.

When it is the second time that the driver program detects the voltagevalue of one of the tap PDs 491, 493, 495 and 497 is continuously lessthan the default threshold value, the micro-control unit 410 won'tperform switch to the corresponding 2×1 optical switches 492, 494, 496and 498 and the step S844 and step S845 are performed. In the step S844,the micro-control unit 410 outputs the unusual information signal tonotify the system firmware that one of the tap PDs 491, 493, 495 and 497occurs an unusual status for the second time. Afterward, in step S845,the micro-control unit 410 stops the operation of polling toward theunusual tap PD 491, 493, 495 or 497 to read its status.

When the ribbon fiber is repaired, the system firmware notifies thedriver to perform the recovery operation for switching all 2×1 opticalswitches 492, 494, 496 and 498 to the original normal path. It should benoted that in the determination method 800 because the micro-controlunit 410 continuously interrogates the voltage status and makes adetermination whether the path is disconnected, some of the computingresources of the micro-control unit 410 are consumed.

On the other hand, the second diagnostic mechanism for determining is ainterrupt mechanism. In the interrupt mechanism, the micro-control unit410 does not usually supervise the status of the tap PDs 491, 493, 495and 497. When the disconnection occurs, the micro-control unit 410 isinterrupted and triggered to confirm the states of the tap PDs 491, 493,495 and 497 and the path switching of the corresponding 2×1 opticalswitches 492, 494, 496 and 498 is performed.

Please refer to FIG. 8C and FIG. 8D. FIG. 8C and FIG. 8D are schematicdiagrams of operations of the micro-control unit 410 executing theinterrupt mechanism in accordance with some embodiments of the presentdisclosure. As shown in FIG. 8C, the tap PDs 491, 493, 495, and 497include interrupt pins ITR1-ITR4 connected to the micro-control unit 410respectively. Taking the tap PD 491 as an example, when the voltagevalue of the tap PD 491 is less than the threshold value for the firsttime, the corresponding interrupt pins ITR1-ITR4 are triggered and atrigger signal TS1 is output to notify the micro-control unit 410. Uponreceiving the trigger signal TS1, the micro-control unit 410 executes acorresponding driver program to perform operations similar to thedetermination method 800.

Specifically, at this time, the micro-control unit 410 first reads thevoltage value of the tap PD 491 to confirm that it is less than thethreshold value. When the voltage value is less than the thresholdvalue, the micro-control unit 410 determines the amount of unusualstatus according to the system record of the system firmware FW.

When it is the first time that the micro-control unit 410 detects thevoltage value of the tap PD 491 is less than the default thresholdvalue, the normal receiving path can be regarded as a fault conditionand the step S842 and step S843 are performed. In the step S842, themicro-control unit 410 outputs the selective signal SS to switch thecorresponding 2×1 optical switches 492, such that the optical signals ofthe backup protection path can pass. In S843, the micro-control unit 410outputs the unusual information signal NS1 to notify the system firmwareFW that the tap PD 491 occurs an unusual status for the first time.

Similarly, as shown in FIG. 8D, when the voltage value of the tap PD 491is less than the threshold value for the second time, the interrupt pinITR1 is triggered again and a trigger signal TS2 is output to notify themicro-control unit 410. At this time, the micro-control unit 410 readsthe voltage value of the tap PD 491 again to confirm that the value isless than the threshold value.

When it is the second time that the micro-control unit 410 detects thevoltage value of one of the tap PD 491 is continuously less than thedefault threshold value, the micro-control unit 410 will not performswitch to the 2×1 optical switch 492 and the step S844 and step S845 areperformed. In the step S844, the micro-control unit 410 outputs theunusual information signal NS2 to notify the system firmware FW that thetap PD 491 occurs an unusual status for the second time.

Similarly, when the ribbon fiber is repaired, the system firmware FWnotifies the micro-control unit 410 and performs the recovery operationthrough the driver program to switch all 2×1 optical switches 492, 494,496 and 498 to the original normal path.

In summary, through the polling mechanism illustrated in FIG. 8B or theinterrupt mechanism illustrated in FIG. 8C and FIG. 8D, themicro-control unit 410 can control the failover sub-module 490 toselectively perform the optical signal transmission via the normal pathor the protection path in order to implement an interconnect protectionpath design between the OSISs 400 a-400 e in the second tier network T2.

Such a result, when one ribbon fiber of the second tier network T2 isdisconnected, the optical signals can still be transmitted to thedestination OSISs 400 a-400 e via the protection path, so that thetransmission of optical signals will not be affected.

Please refer to FIG. 9. FIG. 9 is a schematic diagram of inter-Podstunnel paths between the pods in accordance with some embodiments of thepresent disclosure. In the embodiment in FIG. 9, the rack 900 c in podP1 will transmit optical signals to the racks 900 a and 900 b in anotherpod P2. The software-defined network controller 500 can be configured tobuild two inter-Pod optical tunnels. Specifically, the optical tunnelincludes an optical transmission path and a selected wavelength. Theoptical tunnel between the rack 900 c and the rack 900 a is a path RP1via the rack 900 c passing through the ToR switch TORc, the OADS 200 c,the OSIS 400 a, the OADS 200 a, and the ToR switch TORa to the rack 900a, and is formed by selecting wavelength λ5 to transmit optical signals.

On the other hand, the optical tunnel between the rack 900 c and therack 900 b is a path RP2 via the rack 900 c passing through the ToRswitch TORc, the OADS 200 c, the OSIS 400 a, the OSIS 400 b, the OADS200 b and the ToR switch TORb to the rack 900 b, and is formed byselecting wavelength λ6 to transmit optical signals.

In order to build the two optical tunnels, it is necessary to set theOADSs 200 a-200 c along the path and the 6×4 wavelength selectiveswitches (i.e., the optical switching sub-module 460) of the OSISs 400 aand 400 b to select a specific wavelength to pass.

Please refer to FIG. 10A and FIG. 10B. FIG. 10A and FIG. 10B areschematic diagrams of the setup of the OSIS 400 a and the opticalswitching sub-module 460 of the OSIS 400 b, respectively, in accordancewith some embodiments of the present disclosure. As shown in FIG. 10A,for the path RP1, the optical tunnel can be built by setting one 1×1wavelength selective switch 464 n of the OSIS 400 a and one 1×1wavelength selective switch corresponding to the 2×1 wavelengthselective switch WSS21 in the second transmission module 220 of the OADS200 a at the destination.

On the other hand, as shown in FIG. 10A and FIG. 10B, for the path RP2,the optical tunnel can be built by setting the 1×1 wavelength selectiveswitch 464 a of the OSIS 400 a, the 1×1 wavelength selective switch 464g of the OSIS 400 b and one 1×1 wavelength selective switchcorresponding to the 2×1 wavelength selective switch WSS11 in the firsttransmission module 210 of the OADS 200 b at the destination.

In this way, in the process of transmission, first, the optical signalswith the wavelengths λ5 and λ6 are transmitted, via the correspondingDWDM transceivers on the input-output port of the ToR switch ToRc on therack 900 c, to the corresponding add-port of the first transmissionmodule 210 of the OADS 200 c, combined into one optical fiber throughthe multiplexer 212, duplicated, split via 2×2 first splitter SP11,transmitted northward to the corresponding add-port in the OSIS 400 aand after being combined into one composite optical signal SigU1 by themultiplexer BMUX1, transmitted to the optical switching sub-module 460.At this time, the optical signals with wavelength λ5 and λ6 areduplicated and split through the splitter 462 e into three beams. Onebeam is transmitted eastward to other OSISs, another is transmittedwestward to other OSISs, and finally the other is transmitted southwardto the OADSs 200 a and 200 b at the destination pod P2.

The optical signal transmitted by the OADS 200 a to the southdestination pod P2 passes while the wavelength selective switch 464 nselects the wavelength λ5 to pass, then duplicated and combined, by the5×1 output combiner 466 d, into one optical path, and then the opticalpower is amplified by the optical signal amplifier 468 d. The splitterSPLT2 duplicates, splits the composite signal SigD2 and transmits it toeach OADS in the destination pod P2.

As shown in FIG. 9, the optical signal transmitted to the secondtransmission module 220 of the OADS 200 a passes while the 1×1wavelength selective switch corresponding to a reception in the 2×1wavelength selective switch (please refer to the wavelength selectiveswitch WSS21 in FIG. 2) selects the wavelength λ5 to pass, and istransmitted to the demultiplexer 226. The optical signal with wavelengthλ5 is transmitted from the fifth drop-port of the demultiplexer (can bereferred to the demultiplexer 226 of the second transmission module 220in FIG. 2) in the second transmission module 220 of the OADS 200 a tothe receiver of the corresponding DWDM transceiver on the input-outputport of the ToR switch ToRa on the rack 900 a. The optical signaltransmission from rack 900 c to 900 a is accomplished.

On the other hand, the optical signal transmitted eastward passes whilethe wavelength selective switch 464 a selects the wavelength λ6 to pass,then duplicated and combined, by the 2×1 output combiner 466 a, into oneoptical path, and then the optical power is amplified by the opticalsignal amplifier 468 a as the composite optical signal SigE0. Theoptical signal is transmitted eastward via the interconnection fabricmodule 480 between the OSIS 400 a and 400 b to the OSIS 400 b.

As shown in FIG. 10B, after the optical signal is transmitted to theoptical switching sub-module 460 of the OSIS 400 b, the optical signalwith wavelength λ6 is duplicated and split, by the 1×2 splitter 462 c,into two beams. One beam of the optical signal is transmitted southwardto each OADS in the destination pod P2, and the other beam of theoptical signal is transmitted southward to each OADS in another pod.

The optical signal transmitted southward to the destination pod P2passes while the wavelength selective switch 464 g selects thewavelength λ6 to pass, then duplicated and combined, by the 5×1 outputcombiner 466 c, into one optical path, and then the optical power isamplified by the optical signal amplifier 468 c as the composite opticalsignal SigD1. The splitter SPLT1 duplicates, splits the composite signalSigD1 and transmits it to each OADS in the destination pod P2.

The optical signal transmitted to the first transmission module 210 ofthe OADS 200 b passes while the 1×1 wavelength selective switchcorresponding to a reception in the 2×1 wavelength selective switch(please refer to the wavelength selective switch WSS11 in FIG. 2)selects the wavelength λ6 to pass, and is transmitted to thedemultiplexer 216. The optical signal with wavelength λ6 is transmittedfrom the sixth drop-port of the demultiplexer (can be referred to thedemultiplexer 216 of the first transmission module 210 in FIG. 2) to thereceiver of the corresponding DWDM transceiver on the input-output portof the ToR switch ToRb on the rack 900 b. The optical signaltransmission from rack 900 c to 900 b is accomplished.

In addition, it should be noticed that except the protection paths ofthe OSISs 400 a-400 e in the foregoing second tier network T2, the pathprotection can also be implemented through the independent transmissionrings Ring1 and Ring2 between each OADSs 200 a-200 e in the same pod P1in the first tier network T1 and between the first tier network T1 andthe second tier network T2. When the fiber is disconnected or the fiberconnector is damaged, the protection path can be used to transmit theoptical signal to ensure that the entire optical tunnel network is notaffected by the fiber disconnected. For the sake of explanation, pleaserefer to FIG. 11A. FIG. 11A is a schematic diagram of a design of aprotection path in the pod P1 of the first tier network T1 in accordancewith some embodiments of the present disclosure.

As shown in FIG. 11A, since each pod P1 in the first tier network T1includes a plurality of independent transmission rings Ring1 and Ring2,when one of the rings (for example, the transmission ring Ring1) isdisconnected, the optical signal transmission can be carried out throughother transmission ring Ring2 to achieve the purpose of protection path.In addition, since the fibers of the transmission rings Ring1 and Ring2are independently separated, the probability of simultaneousdisconnection of the two independent fibers is very low.

In this embodiment, when the optical fiber of the transmission ringRing1 corresponding to each of the first transmission modules 210 in thepod P1 is disconnected, the first transmission module 210 of some OADSscannot transmit optical signals westward to other OADSs. For example,the first transmission module 210 of the OADS 200 a cannot transmitoptical signals westward to other OADSs 200 b-200 e in the same pod P1.At this time, the OADSs 200 a-200 e that cannot transmit the opticalsignals by utilizing the transmission ring Ring1, by thesoftware-defined network controller 500 setting the corresponding ToRswitch and the wavelength selective switch through which optical signalsmust pass on the path, transmit the optical signal via the secondtransmission module 220 using the transmission ring Ring2 to transmitoptical signals eastward to other OADSs 200 a-200 e.

Furthermore, in fact, when the transmission ring Ring1 and Ring2 aresimultaneously disconnected and the position where the disconnectionmeets specific criteria, by resetting the wavelength selective switchesWSS11, WSS12, WSS21, WSS22 of each OADS in the pod and each ToR switchthrough the software-defined network controller 500, all the OADSs 200a-200 e can interconnect with each other.

Please refer to FIG. 11B. FIG. 11B is a schematic diagram of a design ofa protection path in the pod P1 of the first tier network T1 inaccordance with some embodiments of the present disclosure. As shown inFIG. 11B, when the transmission ring Ring1 and Ring2 are disconnected atthe same connection point (i.e., between the OADSs 200 a and 200 b), andthere is only one connection point in one pod P1 at which the twotransmission rings Ring1 and Ring2 are disconnected at the same time,the affected OADSs 200 a-200 e can be reset, by the software-definednetwork controller 500 setting the ToR switch and the wavelengthselective switch through which the optical signals pass on the path, andinterconnect to other OADSs 200 a-200 e. Taking the OADSs 200 a and 200b as examples, when the transmission ring Ring1 is disconnected, for theOADS 200 a, the software-defined network controller 500 can set the ToRswitch and the wavelength selective switch through which the opticalsignals pass on the path, so that the optical signal is transmitted withthe wavelength of the second transmission module 220 a eastward by thetransmission ring Ring2 to the OADS 200 b. On the other hand, for theOADS 200 b, the software-defined network controller 500 can set the ToRswitch and the wavelength selective switch through which the opticalsignals pass on the path, so that the optical signal is transmitted withthe wavelength of the first transmission module 210 b westward by thetransmission ring Ring1 to the OADS 200 a, and so on.

In other words, the software-defined network controller 500 can beconfigured to set correspondingly, when optical path of the OADS 200 ato the OADS 200 b on the transmission ring Ring1 is disconnected, theToR switch and the wavelength selective switch through which the opticalsignals pass on the path in order to build the optical tunnel from theOADS 200 a to the OADS 200 b on the transmission ring Ring2 through thesecond transmission modules 220 a-220 e. In some embodiments, thesoftware-defined network controller 500 can be configured to setcorrespondingly, when optical path of the OADS 200 b to the OADS 200 aon the transmission ring Ring2 is disconnected, the ToR switch and thewavelength selective switch through which the optical signals pass onthe path in order to build the optical tunnel from the OADS 200 b to theOADS 200 a on the transmission ring Ring1 through the first transmissionmodules 210 a-210 e.

Please refer to FIG. 12. FIG. 12 is a schematic diagram of a design of aprotection path between the first tier network T1 and the second tiernetwork T2 in accordance with some embodiments of the presentdisclosure. As mentioned in the previous paragraphs, each OADSs 200a-200 e is connected to the adjacent two OSISs 400 a-400 e in the secondtier network T2 via optical fibers. For example, the first transmissionmodule 210 c and the second transmission module 220 c of the OADS 200 chaving one pair of optical fiber separately are connected to the twoadjacent OSISs 400 a and 400 e respectively. Thus, when the opticalfiber connecting the OADS 200 c to the OSIS 400 a is disconnected, theOADS 200 c can utilize another optical path to transmit the opticalsignals to the another OSIS 400 e and then transit them to thedestination OSIS 400 a to achieve another purpose of the protectionpath.

Taking FIG. 12 as an example, the same with the embodiment in FIG. 9, inthe present embodiment, the rack 900 c in the pod P1 will transmitoptical signals to the rack 900 a in another pod P2. It is assumed thatthe optical fiber connecting the first transmission module 210 c of theOADS 200 c and the OSIS 400 a is disconnected. The optical signals canbe transmitted, through the software-defined network controller 500setting the ToR switch and the wavelength selective switch through whichthe optical signals pass on the path to select the wavelength of thesecond transmission module 220 to transmit the optical signal, toanother OSIS 400 e and transited to the destination OADS 200 a. As thepath RP3 shown in the figure, under some circumstance, the opticalsignals may be transmitted first from the OSIS 400 e to another OSIS 400a, and then from the OSIS 400 a to the destination OADS 200 a. Thespecific details of end-to-end transmission are described in theprevious paragraphs and will not be described again.

In other words, the software-defined network controller 500 can furtherbe configured to, when the optical path from the OADS 200 c to the OSIS400 a is disconnected, correspondingly set the ToR switch ToRc to buildthe optical tunnel from the OADS 200 c to the OSIS 400 a (i.e., the pathRP3). Similarly, the software-defined network controller 500 can also beconfigured to, when the optical path from the OADS 200 c to the OSIS 400e is disconnected, correspondingly set the ToR switch ToRc to build theoptical tunnel from the OADS 200 c to the OSIS 400 a.

As a result, whether the optical fiber inside the first tier network T1is disconnected, the optical fiber inside the second tier network T2 isdisconnected, or the longitudinal transmission fiber between the firsttier network T1 and the second tier network T2 is disconnected, theintelligence-defined optical tunnel network system 100 can build opticaltunnels through the redundant path to realize signal transmissionbetween the optical nodes to achieve data transmission between differentservers in different racks.

In some embodiments of the present disclosure, each of the wavelengthselective switches may be implemented by an array design consisted ofone or more 1×1 (1 input and 1 output) wavelength blockers (WB). Thewavelength blocker can be used by digital light processor (DLP)technology to increase the switching speed. In some embodiments, thearray switching time is only about 100 microseconds (μs), so there is afaster and more instant all-optical data center network switchingcapability.

In summary, in various embodiments of the present disclosure, a newnetwork structure is proposed, so that the intelligence-defined opticaltunnel network system 100 can utilize the same wavelength repeatedly tosave wavelength resources. In addition, in the first tier network T1, aring-shaped structure is adopted, the amount of optical nodes in asingle pod can be multiplied arbitrarily without replacing the internalstructure, and the amount of transmission rings in the same pod can bemultiplied as well. The incremental structure with more flexibility isachieved and has better expandability. For example, in the embodimentshown in FIG. 1, the first tier network T1 includes four pod P1-P4, butthe present disclosure is not limited thereof. If the whole system needsto accommodate the information exchange between more racks, the amountof the pod can be increased under the condition of not changing thewhole network structure, for instance, adding the fifth pod orfurthermore adding the sixth pod, and so on. Furthermore, in theembodiment shown in FIG. 1, the amount of optical nodes included in thepod P1 is five, for example, five OADSs 200 a-200 e, but the presentdisclosure in not limited thereof. If the whole system needs toaccommodate the information exchange between more racks, one or morenodes can be added to some pods (or all pods) under the condition of notchanging the whole network structure. For example, when there is a needfor expansion, the pod P1 can further include a new optical node, havinga total of six optical nodes, and the pods P2-P4 can remain having fiveoptical nodes. If there is a need for expansion, new optical nodes canbe added to other pods (i.e., the pod P2), and so on. Through this, theincremental structure is disposed.

On the other hand, the optical switch paths in the second tier networkT2 are simplified, and the protection paths between each of opticalfibers transmission are designed. Whether the optical fiber inside thefirst tier network T1, inside the second tier network T2 or between thefirst tier network T1 and the second tier network T2 is disconnected,the intelligence-defined optical tunnel network system 100 can performoptical signal transmission through the protection paths.

In this way, the intelligence-defined optical tunnel network system 100with low latency, high bandwidth, and low power consumption can berealized. Provide property of reliability, expandability and wavelengthreusability, and low wiring complexity. In addition, based on thecharacteristic of data rate transparency of the optical transmissionsystem, the optical tunnel network can carry optical signals of anytransmission rate within a certain range without changing the design ofthe optical component. Therefore, during upgrading the system, theintelligence-defined optical tunnel network system 100 only needs toreplace the 10G DWDM transceiver with 100G DWDM transceiver forupgrading the wavelength transmission rate from 10 Gbit/s to 100 Gbit/s,which dramatically increases the flexibility of system transmission rateand saves a lot cost of hardware equipment for upgrading.

Although the disclosure has been described in considerable detail withreference to certain embodiments thereof, it will be understood that theembodiments are not intended to limit the disclosure. It will beapparent to those skilled in the art that various modifications andvariations can be made to the structure of the present disclosurewithout departing from the scope or spirit of the disclosure. In view ofthe foregoing, it is intended that the present disclosure covermodifications and variations of this disclosure provided they fallwithin the scope of the following claims.

What is claimed is:
 1. An intelligence-defined optical tunnel networksystem, comprising: a plurality of optical switch interconnectsub-systems, comprising a first optical switch interconnect sub-systemand a second optical switch interconnect sub-system, wherein the firstoptical switch interconnect sub-system transmits a corresponding firstlateral transmission optical signal to the second optical switchinterconnect sub-system through a first line and a corresponding secondlateral transmission optical signal to the second optical switchinterconnect sub-system through a second line, and the second opticalswitch interconnect sub-system comprises: a failover sub-module,configured to output one of the first lateral transmission opticalsignal and the second lateral transmission optical signal in response toa selective signal; and when signal intensity of the first lateraltransmission optical signal is lower than a threshold value, amicro-control unit, configured to output the selective signal to thefailover sub-module in order to control the failover sub-module tooutput the second lateral transmission optical signal.
 2. Theintelligence-defined optical tunnel network system of claim 1, whereinthe failover sub-module comprises: an optical switch, the optical switchconfigured to receive the first lateral transmission optical signal andthe second lateral transmission optical signal from the first opticalswitch interconnect sub-system through the first line and the secondline respectively, and output one of the first lateral transmissionoptical signal and the second lateral transmission optical signal inresponse to the selective signal; and a tap photodetector, the tapphotodetector coupled to the optical switch, and configured to output avoltage value, so that the optical switch performs switch according tothe voltage value.
 3. The intelligence-defined optical tunnel networksystem of claim 2, wherein the micro-control unit is configured tomonitor the value of the tap photodetector, and correspondingly outputthe selective signal to the optical switch when the voltage value islower than a threshold value, so that the optical switch outputs thesecond lateral transmission optical signal.
 4. The intelligence-definedoptical tunnel network system of claim 2, wherein the micro-control unitis configured to execute a driver program to perform steps below:reading the voltage value of the tap photodetector; performingcomparison between the voltage value and a threshold value; when thevoltage value is larger than the threshold value, waiting for a timeinterval and then reading the voltage value of the tap photodetectoragain; and when the voltage value is lower than the threshold value,performing an unusual processing procedure.
 5. The intelligence-definedoptical tunnel network system of claim 4, wherein in the unusualprocessing procedure, the driver program further comprises the stepsbelow: determining a number of times of unusual statuses based on systemrecord of a system firmware; when the unusual status occurs for a firsttime, outputting the selective signal to switch the optical switch, andoutputting an unusual status information signal to notify the systemfirmware that the tap photodetector occurs the unusual status for thefirst time; and when the unusual status occurs for a second time,stopping switching the optical switch, outputting the unusual statusinformation signal to notify the system firmware that the tapphotodetector occurs the unusual status for the second time and stoppingreading the voltage value of the tap photodetector.
 6. Theintelligence-defined optical tunnel network system of claim 2, whereinthe tap photodetector comprises a interrupt pin and the interrupt pin isconnected to the micro-control unit, and the tap photodetector isconfigured to output a trigger signal to the micro-control unit when thevoltage value is less than a threshold value; wherein the micro-controlunit is configured to receive the trigger signal and execute a driverprogram to perform the steps below: reading the voltage value of the tapphotodetector to confirm that the voltage value is lower than thethreshold value; determining a number of unusual status according tosystem record of a system firmware when the voltage value is lower thanthe threshold value; when the unusual status occurs for a first time,outputting the selective signal to switch the optical switch, andoutputting an unusual status information signal to notify the systemfirmware that the tap photodetector occurs the unusual status for thefirst time; and when the unusual status occurs for a second time,stopping switching the optical switch, outputting the unusual statusinformation signal to notify the system firmware that the tapphotodetector occurs the unusual status for the second time.
 7. Theintelligence-defined optical tunnel network system of claim 1, whereinthe first optical switch interconnect sub-system and the second opticalswitch interconnect sub-system comprise respectively: an interconnectionfabric module, configured to connect the first optical switchinterconnect sub-system and the second optical switch interconnectsub-system to build the first line and the second line, wherein theinterconnection fabric module transmits the first lateral transmissionoptical signal to the second optical switch interconnect sub-system in afirst direction and the second lateral transmission optical signal tothe second optical switch interconnect sub-system in a second directiondiffered with the first direction.
 8. The intelligence-defined opticaltunnel network system of claim 7, wherein the first optical switchinterconnect sub-system and the second optical switch interconnectsub-system further comprise respectively: a receiving sub-module,configured to receive a plurality of first uplink transmission opticalsignals and a plurality of third uplink transmission optical signalsfrom a plurality of optical add-drop sub-systems (OADS) respectively; anoutput sub-module, configured to output a plurality of second downlinktransmission optical signals and a plurality of fourth downlinktransmission optical signals to the optical add-drop sub-systemsrespectively; and an optical switching sub-module, coupled with thereceiving sub-module, the output sub-module and the interconnectionfabric module, and configured to transmit optical signals between thereceiving sub-module, the output sub-module and the interconnectionfabric module.
 9. The intelligence-defined optical tunnel network systemof claim 8, wherein the interconnection fabric module comprises: a firstupload terminal and a second upload terminal, a first east outputterminal and a first west output terminal, the first upload terminal andthe second upload terminal coupled to the first east output terminal andthe first west output terminal respectively, and accordingly output theoptical signals received from the optical switching sub-module.
 10. Theintelligence-defined optical tunnel network system of claim 9, whereinthe interconnection fabric module further comprises: a second eastoutput terminal, a second west output terminal, a first east inputterminal and a first west input terminal, wherein the first east inputterminal and the first west input terminal receive the optical signalsfrom the first west output terminal and the first east output terminalin the interconnection fabric module of the adjacent optical switchinterconnect sub-system respectively; and a first interconnect splitterand a second interconnect splitter, wherein the first interconnectsplitter configured to duplicate optical signal received from the firstwest input terminal, and output optical signal through the second eastoutput terminal, and the second interconnect splitter configured toduplicate optical signal received from the first east input terminal,and output optical signal through the second west output terminal. 11.The intelligence-defined optical tunnel network system of claim 10,wherein the interconnection fabric module further comprises: a secondeast input terminal and a second west input terminal, the second eastinput terminal and the second west input terminal configured to receivea lateral transmission optical signals from the second west outputterminal and the second east output terminal in the interconnectionfabric module of the adjacent optical switch interconnect sub-systemrespectively.
 12. The intelligence-defined optical tunnel network systemof claim 11, wherein the failover sub-module is coupled to the firstinterconnect splitter, the second interconnect splitter, the second eastinput terminal and the second west input terminal, and selectivelyoutputs optical signals from the first interconnect splitter, the secondinterconnect splitter, the second east input terminal and the secondwest input terminal to the optical switching sub-module.
 13. Theintelligence-defined optical tunnel network system of claim 9, whereinthe interconnection fabric module further comprises: a first eastprotection output terminal and a first west protection output terminal;and a third interconnect splitter and a fourth interconnect splitter,the third interconnect splitter and the fourth interconnect splittercoupled to the first upload terminal and the second upload terminalrespectively, and configured to duplicate the optical signals receivefrom the optical switching sub-module and output the optical signalsthrough the first east protection output terminal and the first westprotection output terminal respectively.
 14. The intelligence-definedoptical tunnel network system of claim 13, wherein the interconnectionfabric module further comprises: a second east protection outputterminal and a second west protection output terminal; a first eastprotection input terminal and a first west protection input terminal,configured to receive the optical signals from the first west protectionoutput terminal and the first east protection output terminal in theinterconnection fabric module of the adjacent optical switchinterconnect sub-system respectively, and output the optical signalsthrough the second west protection output terminal and the second eastprotection output terminal; a third east protection output terminal anda third west protection output terminal; a second east protection inputterminal and a second west protection input terminal, configured toreceive optical signals from the second west protection output terminaland the second east protection output terminal in the interconnectionfabric module of the adjacent optical switch interconnect sub-systemrespectively, and output the optical signals through the third westprotection output terminal and the third east protection outputterminal; a fourth east protection output terminal and a fourth westprotection output terminal; a third east protection input terminal and athird west protection input terminal, configured to receive opticalsignals from the third west protection output terminal and the thirdeast protection output terminal in the interconnection fabric module ofthe adjacent optical switch interconnect sub-system respectively; afifth interconnect splitter and a sixth interconnect splitter, coupledto the failover sub-module, connected to the third east protection inputterminal and the third west protection input terminal respectively, andconfigured to duplicate optical signals and output optical signals tothe failover sub-module, through the fourth west protection outputterminal and the fourth east protection output terminal; and a fourtheast protection input terminal and a fourth west protection inputterminal, wherein the failover sub-module is coupled to the fourth eastprotection input terminal and the fourth west protection input terminal,and selectively outputs optical signals from the fifth interconnectsplitter, the sixth interconnect splitter, the fourth east protectioninput terminal and the fourth west protection input terminal to theoptical switching sub-module.
 15. A network system control method,comprising: transmitting a first lateral transmission optical signalfrom a first optical switch interconnect sub-system to a second opticalswitch interconnect sub-system through a first line; transmitting asecond lateral transmission optical signal from the first optical switchinterconnect sub-system to the second optical switch interconnectsub-system through a second line; when a signal intensity of the firstlateral transmission optical signal is larger than a threshold value,outputting the first lateral transmission optical signal by a failoversub-module of the second optical switch interconnect sub-system; andwhen the signal intensity of the first lateral transmission opticalsignal is lower than the threshold value, outputting the second lateraltransmission optical signal by the failover sub-module of the secondoptical switch interconnect sub-system.
 16. The network system controlmethod of claim 15, further comprising: when signal intensity of thefirst lateral transmission optical signal is lower than the thresholdvalue, outputting a selective signal to the failover sub-module by amicro-control unit of the second optical switch interconnect sub-systemin order to control the failover sub-module to output the second lateraltransmission optical signal.
 17. The network system control method ofclaim 16, further comprising: outputting a voltage value, according tothe signal intensity of the first lateral transmission optical signal,to the micro-control unit by a tap photodetector of the failoversub-module; and switching an optical switch of the failover sub-moduleaccording to the selective signal, in order to output the second lateraltransmission optical signal.
 18. The network system control method ofclaim 17, further comprising: reading the voltage value of the tapphotodetector by the micro-control unit; performing comparison betweenthe voltage value and the threshold value by the micro-control unit;when the voltage value is larger than the threshold value, waiting for atime interval and then reading the voltage value of the tapphotodetector by the micro-control unit again; and when the voltagevalue is lower than the threshold value, performing an unusualprocessing procedure by the micro-control unit.
 19. The network systemcontrol method of claim 18, further comprising: in the unusualprocessing procedure, determining a number of times of unusual statusbased on system record of a system firmware by the micro-control unit;when the unusual status occurs for a first time, outputting theselective signal by the micro-control unit to switch the optical switchand outputting an unusual status information signal to notify the systemfirmware that the tap photodetector occurs the unusual status for thefirst time; and when the unusual status occurs for a second timestopping switching the optical switch and outputting the unusual statusinformation signal to notify the system firmware that the tapphotodetector occurs the unusual status for the second time by themicro-control unit and stopping reading the voltage value of the tapphotodetector.
 20. The network system control method of claim 17,further comprising: outputting a trigger signal to the micro-controlunit by the tap photodetector when the voltage value is lower than athreshold value; in response to the trigger signal, reading the voltagevalue of the tap photodetector by the micro-control unit to confirm thatthe voltage value is lower than the threshold value; determining anumber of unusual status by the micro-control unit according to systemrecord of a system firmware; when the unusual status occurs for a firsttime, outputting the selective signal to switch the optical switch andoutputting an unusual status information signal to notify the systemfirmware that the tap photodetector occurs the unusual status for thefirst time by the micro-control unit; and when the unusual status occursfor a second time, stopping switching the optical switch and outputtingthe unusual status information signal to notify the system firmware thatthe tap photodetector occurs the unusual status for the second time bythe micro-control unit.